diff --git a/README.md b/README.md
index ba65f78..210695a 100644
--- a/README.md
+++ b/README.md
@@ -54,31 +54,31 @@ dependencies {
 First, you'll define `DataSrc` which manages connections to external data services and creates `DataConn`. Then, you'll define `DataConn` which represents a session-specific connection and implements transactional operations.
 
 ```java
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.DataSrc;
 import com.github.sttk.sabi.DataConn;
 import com.github.sttk.sabi.AsyncGroup;
 
 class FooDataSrc implements DataSrc {
-  @Override public void setup(AsyncGroup ag) throws Exc {}
+  @Override public void setup(AsyncGroup ag) throws Err {}
   @Override public void close() {}
-  @Override public DataConn createDataConn() throws Exc { return new FooDataConn(); }
+  @Override public DataConn createDataConn() throws Err { return new FooDataConn(); }
 }
 
 class FooDataConn implements DataConn {
-  @Override public void commit(AsyncGroup ag) throws Exc {}
+  @Override public void commit(AsyncGroup ag) throws Err {}
   @Override public void rollback(AsyncGroup ag) {}
   @Override public void close(AsyncGroup ag) {}
 }
 
 class BarDataSrc implements DataSrc {
-  @Override public void setup(AsyncGroup ag) throws Exc {}
+  @Override public void setup(AsyncGroup ag) throws Err {}
   @Override public void close() {}
-  @Override public DataConn createDataConn() throws Exc { return new BarDataConn(); }
+  @Override public DataConn createDataConn() throws Err { return new BarDataConn(); }
 }
 
 class BarDataConn implements DataConn {
-  @Override public void commit(AsyncGroup ag) throws Exc {}
+  @Override public void commit(AsyncGroup ag) throws Err {}
   @Override public void rollback(AsyncGroup ag) {}
   @Override public void close(AsyncGroup ag) {}
 }
@@ -89,16 +89,16 @@ class BarDataConn implements DataConn {
 Define interfaces and functions that express your application logic. These interfaces are independent of specific data source implementations, improving testability.
 
 ```java
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.Logic;
 
 interface MyData {
-  String getText() throws Exc;
-  void setText(String text) throws Exc;
+  String getText() throws Err;
+  void setText(String text) throws Err;
 }
 
 class MyLogic implements Logic<MyData> {
-  @Override public void run(MyData data) throws Exc {
+  @Override public void run(MyData data) throws Err {
     String text = data.getText();
     data.setText(text);
   }
@@ -110,11 +110,11 @@ class MyLogic implements Logic<MyData> {
 The `DataAcc` interface abstracts access to data connections. The methods defined here will be used to obtain data connections via `DataHub` and perform actual data operations.
 
 ```java
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.DataAcc;
 
 interface GettingDataAcc extends DataAcc, MyData {
-  @Override default String getText() throws Exc {
+  @Override default String getText() throws Err {
     var conn = getDataConn("foo", FooDataConn.class);
     // ...
     return "output text";
@@ -122,7 +122,7 @@ interface GettingDataAcc extends DataAcc, MyData {
 }
 
 interface SettingDataAcc extends DataAcc, MyData {
-  @Override default void setText(String text) throws Exc {
+  @Override default void setText(String text) throws Err {
     var conn = getDataConn("bar", BarDataConn.class);
     // ...
   }
@@ -134,7 +134,7 @@ interface SettingDataAcc extends DataAcc, MyData {
 The `DataHub` is the central component that manages all `DataSrc` and `DataConn`, providing access to them for your application logic. By implementing the data interface (`MyData`) from step 2 and the `DataAcc` class from step 3 on `DataHub`, you integrate them.
 
 ```java
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.DataHub;
 
 class MyDataHub extends DataHub implements GettingDataAcc, SettingDataAcc {}
@@ -145,7 +145,7 @@ class MyDataHub extends DataHub implements GettingDataAcc, SettingDataAcc {}
 Inside your init function, register your global `DataSrc`. Next, main function calls run function, and inside run function, setup the sabi framework. Then, create an instance of `DataHub` and register the necessary local `DataSrc` using the Uses method. Finally, use the txn method of `DataHub` to execute your defined application logic function (`MyLogic`) within a transaction. This automatically handles transaction commits and rollbacks.
 
 ```java
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.Sabi;
 
 public class Main {
diff --git a/pom.xml b/pom.xml
index 86e7e60..95297ba 100644
--- a/pom.xml
+++ b/pom.xml
@@ -50,7 +50,7 @@
     <dependency>
       <groupId>io.github.sttk</groupId>
       <artifactId>errs</artifactId>
-      <version>0.1.0</version>
+      <version>0.2.0</version>
       <scope>compile</scope>
     </dependency>
     <dependency>
diff --git a/src/main/java/com/github/sttk/sabi/AsyncGroup.java b/src/main/java/com/github/sttk/sabi/AsyncGroup.java
index 82ffbe3..cdb8ee0 100644
--- a/src/main/java/com/github/sttk/sabi/AsyncGroup.java
+++ b/src/main/java/com/github/sttk/sabi/AsyncGroup.java
@@ -1,6 +1,6 @@
 /*
  * AsyncGroup.java
- * Copyright (C) 2023-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2023-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi;
 
@@ -16,14 +16,14 @@
 public interface AsyncGroup {
 
   /**
-   * Represents the reason for a new {@link com.github.sttk.errs.Exc} exception object when an
+   * Represents the reason for a new {@link com.github.sttk.errs.Err} exception object when an
    * exception occurred during the execution of a {@link Runner} and the exception class was not the
-   * {@link com.github.sttk.errs.Exc}.
+   * {@link com.github.sttk.errs.Err}.
    */
   record RunnerFailed() {}
 
   /**
-   * Represents the reason for an {@link com.github.sttk.errs.Exc} exception object when the
+   * Represents the reason for an {@link com.github.sttk.errs.Err} exception object when the
    * creation of a thread for asynchronous execution of a {@link Runner} fails.
    */
   record RunnerInterrupted() {}
diff --git a/src/main/java/com/github/sttk/sabi/DataAcc.java b/src/main/java/com/github/sttk/sabi/DataAcc.java
index e8b1372..2a6855c 100644
--- a/src/main/java/com/github/sttk/sabi/DataAcc.java
+++ b/src/main/java/com/github/sttk/sabi/DataAcc.java
@@ -1,10 +1,10 @@
 /*
  * DataAcc.java
- * Copyright (C) 2023-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2023-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 
 /**
  * An interface designed for implementing data access operations through default methods in its
@@ -25,7 +25,7 @@ public interface DataAcc {
    * @param name The name identifying the specific data connection to retrieve.
    * @param cls The {@link Class} object representing the type of the desired data connection.
    * @return A data connection object of the specified type.
-   * @throws Exc if an error occurs while obtaining the data connection.
+   * @throws Err if an error occurs while obtaining the data connection.
    */
-  <C extends DataConn> C getDataConn(String name, Class<C> cls) throws Exc;
+  <C extends DataConn> C getDataConn(String name, Class<C> cls) throws Err;
 }
diff --git a/src/main/java/com/github/sttk/sabi/DataConn.java b/src/main/java/com/github/sttk/sabi/DataConn.java
index 1b2ed07..6240219 100644
--- a/src/main/java/com/github/sttk/sabi/DataConn.java
+++ b/src/main/java/com/github/sttk/sabi/DataConn.java
@@ -1,10 +1,10 @@
 /*
  * DataConn.java
- * Copyright (C) 2022-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2022-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 
 /**
  * The interface that abstracts a connection per session to an external data service, such as a
@@ -25,18 +25,18 @@ public interface DataConn {
    *
    * @param ag An {@link AsyncGroup} that can be used to perform asynchronous operations if the
    *     commit process is time-consuming.
-   * @throws Exc if an error occurs during the commit operation.
+   * @throws Err if an error occurs during the commit operation.
    */
-  void commit(AsyncGroup ag) throws Exc;
+  void commit(AsyncGroup ag) throws Err;
 
   /**
    * Performs any necessary pre-commit operations. This method is called before the {@link
    * #commit(AsyncGroup)} method.
    *
    * @param ag An {@link AsyncGroup} that can be used for asynchronous pre-commit tasks.
-   * @throws Exc if an error occurs during the pre-commit operation.
+   * @throws Err if an error occurs during the pre-commit operation.
    */
-  default void preCommit(AsyncGroup ag) throws Exc {}
+  default void preCommit(AsyncGroup ag) throws Err {}
 
   /**
    * Performs any necessary post-commit operations. This method is called after the {@link
diff --git a/src/main/java/com/github/sttk/sabi/DataHub.java b/src/main/java/com/github/sttk/sabi/DataHub.java
index 981179b..d817061 100644
--- a/src/main/java/com/github/sttk/sabi/DataHub.java
+++ b/src/main/java/com/github/sttk/sabi/DataHub.java
@@ -1,10 +1,10 @@
 /*
  * DataHub.java
- * Copyright (C) 2022-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2022-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.internal.DataHubInner;
 import java.util.Map;
 
@@ -25,7 +25,7 @@ public class DataHub implements DataAcc, AutoCloseable {
    * @param errors A map containing the names of the data sources and the corresponding exceptions
    *     that occurred during their setup.
    */
-  public record FailToSetupGlobalDataSrcs(Map<String, Exc> errors) {}
+  public record FailToSetupGlobalDataSrcs(Map<String, Err> errors) {}
 
   /**
    * Represents an error reason that occurred when failing to set up local {@link DataSrc}
@@ -34,7 +34,7 @@ public record FailToSetupGlobalDataSrcs(Map<String, Exc> errors) {}
    * @param errors A map containing the names of the data sources and the corresponding exceptions
    *     that occurred during their setup.
    */
-  public record FailToSetupLocalDataSrcs(Map<String, Exc> errors) {}
+  public record FailToSetupLocalDataSrcs(Map<String, Err> errors) {}
 
   /**
    * Represents an error reason that occurred when failing to commit one or more {@link DataConn}
@@ -43,7 +43,7 @@ public record FailToSetupLocalDataSrcs(Map<String, Exc> errors) {}
    * @param errors A map containing the names of the data connections and the corresponding
    *     exceptions that occurred during their commit.
    */
-  public record FailToCommitDataConn(Map<String, Exc> errors) {}
+  public record FailToCommitDataConn(Map<String, Err> errors) {}
 
   /**
    * Represents an error reason that occurred when failing to pre-commit one or more {@link
@@ -52,7 +52,7 @@ public record FailToCommitDataConn(Map<String, Exc> errors) {}
    * @param errors A map containing the names of the data connections and the corresponding
    *     exceptions that occurred during their pre-commit.
    */
-  public record FailToPreCommitDataConn(Map<String, Exc> errors) {}
+  public record FailToPreCommitDataConn(Map<String, Err> errors) {}
 
   /**
    * Represents an error reason where no {@link DataSrc} was found to create a {@link DataConn} with
@@ -128,11 +128,11 @@ public void disuses(String name) {
    * @param name The name of the data source from which to get the connection.
    * @param cls The {@link Class} object representing the desired type of the data connection.
    * @return A {@link DataConn} instance of the specified type.
-   * @throws Exc if no data source is found, if the connection cannot be created, if the created
+   * @throws Err if no data source is found, if the connection cannot be created, if the created
    *     connection is null, or if the connection cannot be cast to the specified class.
    */
   @Override
-  public <C extends DataConn> C getDataConn(String name, Class<C> cls) throws Exc {
+  public <C extends DataConn> C getDataConn(String name, Class<C> cls) throws Err {
     return inner.getDataConn(name, cls);
   }
 
@@ -146,11 +146,11 @@ public void close() {
     inner.close();
   }
 
-  void begin() throws Exc {
+  void begin() throws Err {
     inner.begin();
   }
 
-  void commit() throws Exc {
+  void commit() throws Err {
     inner.commit();
   }
 
diff --git a/src/main/java/com/github/sttk/sabi/DataSrc.java b/src/main/java/com/github/sttk/sabi/DataSrc.java
index 1237c5a..0067ba8 100644
--- a/src/main/java/com/github/sttk/sabi/DataSrc.java
+++ b/src/main/java/com/github/sttk/sabi/DataSrc.java
@@ -1,10 +1,10 @@
 /*
  * DataSrc.java
- * Copyright (C) 2022-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2022-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 
 /**
  * The interface that abstracts a data source responsible for managing connections to external data
@@ -21,9 +21,9 @@ public interface DataSrc {
    *
    * @param ag An {@link AsyncGroup} that can be used for asynchronous setup operations, especially
    *     if initialization is time-consuming.
-   * @throws Exc if an error occurs during the setup process.
+   * @throws Err if an error occurs during the setup process.
    */
-  void setup(AsyncGroup ag) throws Exc;
+  void setup(AsyncGroup ag) throws Err;
 
   /**
    * Closes the data source, releasing all resources and shutting down connections managed by this
@@ -38,7 +38,7 @@ public interface DataSrc {
    * connection.
    *
    * @return A new {@link DataConn} instance for a session.
-   * @throws Exc if an error occurs while creating the data connection.
+   * @throws Err if an error occurs while creating the data connection.
    */
-  DataConn createDataConn() throws Exc;
+  DataConn createDataConn() throws Err;
 }
diff --git a/src/main/java/com/github/sttk/sabi/Logic.java b/src/main/java/com/github/sttk/sabi/Logic.java
index 53b449b..0ff1fce 100644
--- a/src/main/java/com/github/sttk/sabi/Logic.java
+++ b/src/main/java/com/github/sttk/sabi/Logic.java
@@ -1,10 +1,10 @@
 /*
  * Logic.java
- * Copyright (C) 2022-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2022-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 
 /**
  * Represents the application's business logic, designed to separate data access concerns from the
@@ -15,7 +15,7 @@
  * {@link #run(Object)} method should not contain any direct data access code; instead, it should
  * delegate such operations to methods of the {@code D} object.
  *
- * <p>If an exceptional condition occurs during the execution of the logic, an {@link Exc} object
+ * <p>If an exceptional condition occurs during the execution of the logic, an {@link Err} object
  * should be thrown.
  *
  * @param <D> The type of the data access object through which data operations are performed.
@@ -27,7 +27,7 @@ public interface Logic<D> {
    * on the {@code data} object for all data access needs.
    *
    * @param data The data access object, providing methods for interacting with data.
-   * @throws Exc if an error or exceptional condition occurs during the logic execution.
+   * @throws Err if an error or exceptional condition occurs during the logic execution.
    */
-  void run(D data) throws Exc;
+  void run(D data) throws Err;
 }
diff --git a/src/main/java/com/github/sttk/sabi/Runner.java b/src/main/java/com/github/sttk/sabi/Runner.java
index 760ac7f..a75277e 100644
--- a/src/main/java/com/github/sttk/sabi/Runner.java
+++ b/src/main/java/com/github/sttk/sabi/Runner.java
@@ -1,10 +1,10 @@
 /*
  * Runner.java
- * Copyright (C) 2022-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2022-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 
 /** {@code Runner} is the interface that runs any procedure. */
 @FunctionalInterface
@@ -12,9 +12,9 @@ public interface Runner {
 
   /**
    * Runs the procedure that this instance represents. This method takes no argument and returns
-   * nothing. And this method throws an {@link Exc} exception if this method failed.
+   * nothing. And this method throws an {@link Err} exception if this method failed.
    *
-   * @throws Exc If this method failed.
+   * @throws Err If this method failed.
    */
-  void run() throws Exc;
+  void run() throws Err;
 }
diff --git a/src/main/java/com/github/sttk/sabi/Sabi.java b/src/main/java/com/github/sttk/sabi/Sabi.java
index 022c042..796bf07 100644
--- a/src/main/java/com/github/sttk/sabi/Sabi.java
+++ b/src/main/java/com/github/sttk/sabi/Sabi.java
@@ -1,10 +1,10 @@
 /*
  * Sabi.java
- * Copyright (C) 2022-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2022-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.internal.DataHubInner;
 
 /**
@@ -66,9 +66,9 @@ public static void uses(String name, DataSrc ds) {
    *
    * @return An {@link AutoCloseable} object that, when closed, will trigger the global close
    *     operation.
-   * @throws Exc if an error occurs during the setup of any {@link DataSrc}.
+   * @throws Err if an error occurs during the setup of any {@link DataSrc}.
    */
-  public static AutoCloseable setup() throws Exc {
+  public static AutoCloseable setup() throws Err {
     return DataHubInner.setupGlobals();
   }
 
@@ -82,22 +82,22 @@ public static AutoCloseable setup() throws Exc {
    * @param logic The application logic to execute.
    * @param hub An instance of a DataHub subclass that inherits the data interface for logic
    *     arguments.
-   * @throws Exc if an {@link Exc} or {@link RuntimeException} occurs during logic execution or if
+   * @throws Err if an {@link Err} or {@link RuntimeException} occurs during logic execution or if
    *     the {@code DataHub} cannot be cast to the expected data access type.
    */
-  public static <D> void run(Logic<D> logic, DataHub hub) throws Exc {
+  public static <D> void run(Logic<D> logic, DataHub hub) throws Err {
     D data;
     try {
       @SuppressWarnings("unchecked")
       D d = (D) hub;
       data = d;
     } catch (Exception e) {
-      throw new Exc(new FailToCastDataHub(hub.getClass().getName()));
+      throw new Err(new FailToCastDataHub(hub.getClass().getName()));
     }
     try {
       hub.begin();
       logic.run(data);
-    } catch (Exc | RuntimeException e) {
+    } catch (Err | RuntimeException e) {
       throw e;
     } finally {
       hub.end();
@@ -108,7 +108,7 @@ public static <D> void run(Logic<D> logic, DataHub hub) throws Exc {
    * Executes the provided application {@link Logic} within a transactional context. The {@code
    * DataHub} instance in the parameter is passed as the data access object {@code D} to the {@link
    * Logic}'s {@code run} method. If the logic completes successfully, a commit operation is
-   * attempted. If any {@link Exc}, {@link RuntimeException}, or {@link Error} occurs, a rollback
+   * attempted. If any {@link Err}, {@link RuntimeException}, or {@link Error} occurs, a rollback
    * operation is performed.
    *
    * @param <D> The type of the data access object, which typically is {@code DataHub} or an
@@ -116,23 +116,23 @@ public static <D> void run(Logic<D> logic, DataHub hub) throws Exc {
    * @param logic The application logic to execute transactionally.
    * @param hub An instance of a DataHub subclass that inherits the data interface for logic
    *     arguments.
-   * @throws Exc if an {@link Exc}, {@link RuntimeException}, or {@link Error} occurs during logic
+   * @throws Err if an {@link Err}, {@link RuntimeException}, or {@link Error} occurs during logic
    *     execution, pre-commit, or commit. The original exception is re-thrown after rollback.
    */
-  public static <D> void txn(Logic<D> logic, DataHub hub) throws Exc {
+  public static <D> void txn(Logic<D> logic, DataHub hub) throws Err {
     D data;
     try {
       @SuppressWarnings("unchecked")
       D d = (D) hub;
       data = d;
     } catch (Exception e) {
-      throw new Exc(new FailToCastDataHub(hub.getClass().getName()));
+      throw new Err(new FailToCastDataHub(hub.getClass().getName()));
     }
     try {
       hub.begin();
       logic.run(data);
       hub.commit();
-    } catch (Exc | RuntimeException | Error e) {
+    } catch (Err | RuntimeException | Error e) {
       hub.rollback();
       throw e;
     } finally {
diff --git a/src/main/java/com/github/sttk/sabi/internal/AsyncGroupImpl.java b/src/main/java/com/github/sttk/sabi/internal/AsyncGroupImpl.java
index 5f34e8e..f598396 100644
--- a/src/main/java/com/github/sttk/sabi/internal/AsyncGroupImpl.java
+++ b/src/main/java/com/github/sttk/sabi/internal/AsyncGroupImpl.java
@@ -1,17 +1,17 @@
 /*
  * AsyncGroupImpl.java
- * Copyright (C) 2023-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2023-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi.internal;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.AsyncGroup;
 import com.github.sttk.sabi.Runner;
 import java.util.Map;
 
 public class AsyncGroupImpl implements AsyncGroup {
-  private ExcEntry excHead;
-  private ExcEntry excLast;
+  private ErrEntry errHead;
+  private ErrEntry errLast;
   private VthEntry vthHead;
   private VthEntry vthLast;
   String name;
@@ -27,8 +27,8 @@ public void add(final Runner runner) {
                 () -> {
                   try {
                     runner.run();
-                  } catch (Exc | RuntimeException e) {
-                    addExc(name, e);
+                  } catch (Err | RuntimeException e) {
+                    addErr(name, e);
                   }
                 });
 
@@ -42,34 +42,34 @@ public void add(final Runner runner) {
     }
   }
 
-  synchronized void addExc(String name, Exception e) {
-    var exc = (e instanceof Exc) ? Exc.class.cast(e) : new Exc(new RunnerFailed(), e);
-    var ent = new ExcEntry(name, exc);
+  synchronized void addErr(String name, Exception e) {
+    var err = (e instanceof Err) ? Err.class.cast(e) : new Err(new RunnerFailed(), e);
+    var ent = new ErrEntry(name, err);
 
-    if (this.excLast == null) {
-      this.excHead = ent;
-      this.excLast = ent;
+    if (this.errLast == null) {
+      this.errHead = ent;
+      this.errLast = ent;
     } else {
-      this.excLast.next = ent;
-      this.excLast = ent;
+      this.errLast.next = ent;
+      this.errLast = ent;
     }
   }
 
-  void joinAndPutExcsInto(Map<String, Exc> excMap) {
+  void joinAndPutErrsInto(Map<String, Err> errMap) {
     for (var ent = this.vthHead; ent != null; ent = ent.next) {
       try {
         ent.thread.join();
       } catch (InterruptedException e) {
-        addExc(ent.name, new Exc(new RunnerInterrupted(), e));
+        addErr(ent.name, new Err(new RunnerInterrupted(), e));
       }
     }
-    for (var ent = this.excHead; ent != null; ent = ent.next) {
-      excMap.put(ent.name, ent.exc);
+    for (var ent = this.errHead; ent != null; ent = ent.next) {
+      errMap.put(ent.name, ent.err);
     }
     clear();
   }
 
-  void joinAndIgnoreExcs() {
+  void joinAndIgnoreErrs() {
     for (var ent = this.vthHead; ent != null; ent = ent.next) {
       try {
         ent.thread.join();
@@ -80,21 +80,21 @@ void joinAndIgnoreExcs() {
   }
 
   void clear() {
-    this.excHead = null;
-    this.excLast = null;
+    this.errHead = null;
+    this.errLast = null;
     this.vthHead = null;
     this.vthLast = null;
   }
 }
 
-class ExcEntry {
+class ErrEntry {
   final String name;
-  final Exc exc;
-  ExcEntry next;
+  final Err err;
+  ErrEntry next;
 
-  ExcEntry(String name, Exc exc) {
+  ErrEntry(String name, Err err) {
     this.name = name;
-    this.exc = exc;
+    this.err = err;
   }
 }
 
diff --git a/src/main/java/com/github/sttk/sabi/internal/DataHubInner.java b/src/main/java/com/github/sttk/sabi/internal/DataHubInner.java
index 369a533..1ed7be8 100644
--- a/src/main/java/com/github/sttk/sabi/internal/DataHubInner.java
+++ b/src/main/java/com/github/sttk/sabi/internal/DataHubInner.java
@@ -1,10 +1,10 @@
 /*
  * DataHubInner.java
- * Copyright (C) 2022-2025 Takayuki Sato. All Rights Reserved.
+ * Copyright (C) 2022-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi.internal;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.DataConn;
 import com.github.sttk.sabi.DataHub;
 import com.github.sttk.sabi.DataSrc;
@@ -24,12 +24,12 @@ public static void usesGlobal(String name, DataSrc ds) {
     }
   }
 
-  public static AutoCloseable setupGlobals() throws Exc {
+  public static AutoCloseable setupGlobals() throws Err {
     if (GLOBAL_DATA_SRCS_FIXED.compareAndSet(false, true)) {
-      var excMap = GLOBAL_DATA_SRC_LIST.setupDataSrcs();
-      if (!excMap.isEmpty()) {
+      var errMap = GLOBAL_DATA_SRC_LIST.setupDataSrcs();
+      if (!errMap.isEmpty()) {
         GLOBAL_DATA_SRC_LIST.closeDataSrcs();
-        throw new Exc(new DataHub.FailToSetupGlobalDataSrcs(excMap));
+        throw new Err(new DataHub.FailToSetupGlobalDataSrcs(errMap));
       }
     }
     return new AutoShutdown();
@@ -83,19 +83,19 @@ public void close() {
     this.localDataSrcList.closeDataSrcs();
   }
 
-  public void begin() throws Exc {
+  public void begin() throws Err {
     this.fixed = true;
 
-    var excMap = this.localDataSrcList.setupDataSrcs();
+    var errMap = this.localDataSrcList.setupDataSrcs();
     this.localDataSrcList.copyContainerPtrsDidSetupInto(this.dataSrcMap);
 
-    if (!excMap.isEmpty()) {
-      throw new Exc(new DataHub.FailToSetupLocalDataSrcs(excMap));
+    if (!errMap.isEmpty()) {
+      throw new Err(new DataHub.FailToSetupLocalDataSrcs(errMap));
     }
   }
 
-  public void commit() throws Exc {
-    var excMap = new HashMap<String, Exc>();
+  public void commit() throws Err {
+    var errMap = new HashMap<String, Err>();
 
     var ag = new AsyncGroupImpl();
     var ptr = this.dataConnList.head;
@@ -103,19 +103,19 @@ public void commit() throws Exc {
       ag.name = ptr.name;
       try {
         ptr.conn.preCommit(ag);
-      } catch (Exc e) {
-        excMap.put(ptr.name, e);
+      } catch (Err e) {
+        errMap.put(ptr.name, e);
         break;
       } catch (RuntimeException e) {
-        excMap.put(ptr.name, new Exc(new DataHub.RuntimeExceptionOccurred(), e));
+        errMap.put(ptr.name, new Err(new DataHub.RuntimeExceptionOccurred(), e));
         break;
       }
       ptr = ptr.next;
     }
-    ag.joinAndPutExcsInto(excMap);
+    ag.joinAndPutErrsInto(errMap);
 
-    if (!excMap.isEmpty()) {
-      throw new Exc(new DataHub.FailToPreCommitDataConn(excMap));
+    if (!errMap.isEmpty()) {
+      throw new Err(new DataHub.FailToPreCommitDataConn(errMap));
     }
 
     ag = new AsyncGroupImpl();
@@ -124,19 +124,19 @@ public void commit() throws Exc {
       ag.name = ptr.name;
       try {
         ptr.conn.commit(ag);
-      } catch (Exc e) {
-        excMap.put(ptr.name, e);
+      } catch (Err e) {
+        errMap.put(ptr.name, e);
         break;
       } catch (RuntimeException e) {
-        excMap.put(ptr.name, new Exc(new DataHub.RuntimeExceptionOccurred(), e));
+        errMap.put(ptr.name, new Err(new DataHub.RuntimeExceptionOccurred(), e));
         break;
       }
       ptr = ptr.next;
     }
-    ag.joinAndPutExcsInto(excMap);
+    ag.joinAndPutErrsInto(errMap);
 
-    if (!excMap.isEmpty()) {
-      throw new Exc(new DataHub.FailToCommitDataConn(excMap));
+    if (!errMap.isEmpty()) {
+      throw new Err(new DataHub.FailToCommitDataConn(errMap));
     }
 
     ag = new AsyncGroupImpl();
@@ -147,7 +147,7 @@ public void commit() throws Exc {
       ptr = ptr.next;
     }
 
-    ag.joinAndIgnoreExcs();
+    ag.joinAndIgnoreErrs();
   }
 
   public void rollback() {
@@ -163,7 +163,7 @@ public void rollback() {
       ptr = ptr.next;
     }
 
-    ag.joinAndIgnoreExcs();
+    ag.joinAndIgnoreErrs();
   }
 
   public void end() {
@@ -172,36 +172,36 @@ public void end() {
     this.fixed = false;
   }
 
-  public <C extends DataConn> C getDataConn(String name, Class<C> cls) throws Exc {
+  public <C extends DataConn> C getDataConn(String name, Class<C> cls) throws Err {
     var connPtr = this.dataConnMap.get(name);
     if (connPtr != null) {
       try {
         return cls.cast(connPtr.conn);
       } catch (Exception e) {
-        throw new Exc(new DataHub.FailToCastDataConn(name, cls.getName()), e);
+        throw new Err(new DataHub.FailToCastDataConn(name, cls.getName()), e);
       }
     }
 
     var dsPtr = this.dataSrcMap.get(name);
     if (dsPtr == null) {
-      throw new Exc(new DataHub.NoDataSrcToCreateDataConn(name, cls.getName()));
+      throw new Err(new DataHub.NoDataSrcToCreateDataConn(name, cls.getName()));
     }
 
     DataConn conn;
     try {
       conn = dsPtr.ds.createDataConn();
-    } catch (Exc | RuntimeException e) {
-      throw new Exc(new DataHub.FailToCreateDataConn(name, cls.getName()));
+    } catch (Err | RuntimeException e) {
+      throw new Err(new DataHub.FailToCreateDataConn(name, cls.getName()));
     }
     if (conn == null) {
-      throw new Exc(new DataHub.CreatedDataConnIsNull(name, cls.getName()));
+      throw new Err(new DataHub.CreatedDataConnIsNull(name, cls.getName()));
     }
 
     C c;
     try {
       c = cls.cast(conn);
     } catch (Exception e) {
-      throw new Exc(new DataHub.FailToCastDataConn(name, cls.getName()), e);
+      throw new Err(new DataHub.FailToCastDataConn(name, cls.getName()), e);
     }
 
     connPtr = new DataConnContainer(name, c);
diff --git a/src/main/java/com/github/sttk/sabi/internal/DataSrcList.java b/src/main/java/com/github/sttk/sabi/internal/DataSrcList.java
index 297f505..b9f32cb 100644
--- a/src/main/java/com/github/sttk/sabi/internal/DataSrcList.java
+++ b/src/main/java/com/github/sttk/sabi/internal/DataSrcList.java
@@ -1,10 +1,10 @@
 /*
- * DataSrcContainer.java
- * Copyright (C) 2025 Takayuki Sato. All Rights Reserved.
+ * DataSrcList.java
+ * Copyright (C) 2025-2026 Takayuki Sato. All Rights Reserved.
  */
 package com.github.sttk.sabi.internal;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.DataSrc;
 import java.util.HashMap;
 import java.util.Map;
@@ -122,11 +122,11 @@ void addDataSrc(String name, DataSrc ds) {
     this.appendContainerPtrNotSetup(ptr);
   }
 
-  Map<String, Exc> setupDataSrcs() {
-    var excMap = new HashMap<String, Exc>();
+  Map<String, Err> setupDataSrcs() {
+    var errMap = new HashMap<String, Err>();
 
     if (this.notSetupHead == null) {
-      return excMap;
+      return errMap;
     }
 
     var ag = new AsyncGroupImpl();
@@ -136,28 +136,28 @@ Map<String, Exc> setupDataSrcs() {
       ag.name = ptr.name;
       try {
         ptr.ds.setup(ag);
-      } catch (Exc exc) {
-        excMap.put(ptr.name, exc);
+      } catch (Err err) {
+        errMap.put(ptr.name, err);
         break;
       }
       ptr = ptr.next;
     }
 
-    ag.joinAndPutExcsInto(excMap);
+    ag.joinAndPutErrsInto(errMap);
 
     var firstPtrNotSetupYet = ptr;
 
     ptr = this.notSetupHead;
     while (ptr != null && ptr != firstPtrNotSetupYet) {
       var next = ptr.next;
-      if (!excMap.containsKey(ptr.name)) {
+      if (!errMap.containsKey(ptr.name)) {
         this.removeContainerPtrNotSetup(ptr);
         this.appendContainerPtrDidSetup(ptr);
       }
       ptr = next;
     }
 
-    return excMap;
+    return errMap;
   }
 
   void closeDataSrcs() {
diff --git a/src/test/java/com/github/sttk/sabi/internal/AsyncGroupImplTest.java b/src/test/java/com/github/sttk/sabi/internal/AsyncGroupImplTest.java
index 589c27d..09e4d11 100644
--- a/src/test/java/com/github/sttk/sabi/internal/AsyncGroupImplTest.java
+++ b/src/test/java/com/github/sttk/sabi/internal/AsyncGroupImplTest.java
@@ -3,7 +3,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.fail;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.Runner;
 import java.util.HashMap;
 import org.junit.jupiter.api.Test;
@@ -15,8 +15,8 @@ private AsyncGroupImplTest() {}
   void zero() {
     var ag = new AsyncGroupImpl();
 
-    var m = new HashMap<String, Exc>();
-    ag.joinAndPutExcsInto(m);
+    var m = new HashMap<String, Err>();
+    ag.joinAndPutErrsInto(m);
     assertThat(m).hasSize(0);
   }
 
@@ -38,8 +38,8 @@ void ok() {
     ag.add(fn);
     assertThat(executed[0]).isFalse();
 
-    var m = new HashMap<String, Exc>();
-    ag.joinAndPutExcsInto(m);
+    var m = new HashMap<String, Err>();
+    ag.joinAndPutErrsInto(m);
     assertThat(m).hasSize(0);
     assertThat(executed[0]).isTrue();
   }
@@ -58,15 +58,15 @@ record FailToDoSomething() {}
           } catch (Exception e) {
           }
           executed[0] = true;
-          throw new Exc(new FailToDoSomething());
+          throw new Err(new FailToDoSomething());
         };
 
     ag.name = "foo";
     ag.add(fn);
     assertThat(executed[0]).isFalse();
 
-    var m = new HashMap<String, Exc>();
-    ag.joinAndPutExcsInto(m);
+    var m = new HashMap<String, Err>();
+    ag.joinAndPutErrsInto(m);
     assertThat(m).hasSize(1);
     assertThat(executed[0]).isTrue();
 
@@ -93,7 +93,7 @@ record Reason2() {}
           } catch (Exception e) {
           }
           executed[0] = true;
-          throw new Exc(new Reason0());
+          throw new Err(new Reason0());
         };
     Runner fn1 =
         () -> {
@@ -102,7 +102,7 @@ record Reason2() {}
           } catch (Exception e) {
           }
           executed[1] = true;
-          throw new Exc(new Reason1());
+          throw new Err(new Reason1());
         };
     Runner fn2 =
         () -> {
@@ -111,7 +111,7 @@ record Reason2() {}
           } catch (Exception e) {
           }
           executed[2] = true;
-          throw new Exc(new Reason2());
+          throw new Err(new Reason2());
         };
 
     ag.name = "foo0";
@@ -121,8 +121,8 @@ record Reason2() {}
     ag.name = "foo2";
     ag.add(fn2);
 
-    var m = new HashMap<String, Exc>();
-    ag.joinAndPutExcsInto(m);
+    var m = new HashMap<String, Err>();
+    ag.joinAndPutErrsInto(m);
     assertThat(m).hasSize(3);
     assertThat(executed[0]).isTrue();
     assertThat(executed[1]).isTrue();
@@ -130,13 +130,13 @@ record Reason2() {}
 
     assertThat(m.get("foo0").toString())
         .isEqualTo(
-            "com.github.sttk.errs.Exc { reason = com.github.sttk.sabi.internal.AsyncGroupImplTest$1Reason0 Reason0[], file = AsyncGroupImplTest.java, line = 96 }");
+            "com.github.sttk.errs.Err { reason = com.github.sttk.sabi.internal.AsyncGroupImplTest$1Reason0 Reason0[], file = AsyncGroupImplTest.java, line = 96 }");
     assertThat(m.get("foo1").toString())
         .isEqualTo(
-            "com.github.sttk.errs.Exc { reason = com.github.sttk.sabi.internal.AsyncGroupImplTest$1Reason1 Reason1[], file = AsyncGroupImplTest.java, line = 105 }");
+            "com.github.sttk.errs.Err { reason = com.github.sttk.sabi.internal.AsyncGroupImplTest$1Reason1 Reason1[], file = AsyncGroupImplTest.java, line = 105 }");
     assertThat(m.get("foo2").toString())
         .isEqualTo(
-            "com.github.sttk.errs.Exc { reason = com.github.sttk.sabi.internal.AsyncGroupImplTest$1Reason2 Reason2[], file = AsyncGroupImplTest.java, line = 114 }");
+            "com.github.sttk.errs.Err { reason = com.github.sttk.sabi.internal.AsyncGroupImplTest$1Reason2 Reason2[], file = AsyncGroupImplTest.java, line = 114 }");
   }
 
   @Test
@@ -156,7 +156,7 @@ record Reason2() {}
           } catch (Exception e) {
           }
           executed[0] = true;
-          throw new Exc(new Reason0());
+          throw new Err(new Reason0());
         };
     Runner fn1 =
         () -> {
@@ -165,7 +165,7 @@ record Reason2() {}
           } catch (Exception e) {
           }
           executed[1] = true;
-          throw new Exc(new Reason1());
+          throw new Err(new Reason1());
         };
     Runner fn2 =
         () -> {
@@ -174,7 +174,7 @@ record Reason2() {}
           } catch (Exception e) {
           }
           executed[2] = true;
-          throw new Exc(new Reason2());
+          throw new Err(new Reason2());
         };
 
     ag.name = "foo0";
@@ -184,7 +184,7 @@ record Reason2() {}
     ag.name = "foo2";
     ag.add(fn2);
 
-    ag.joinAndIgnoreExcs();
+    ag.joinAndIgnoreErrs();
     assertThat(executed[0]).isTrue();
     assertThat(executed[1]).isTrue();
     assertThat(executed[2]).isTrue();
diff --git a/src/test/java/com/github/sttk/sabi/internal/DataAccTest.java b/src/test/java/com/github/sttk/sabi/internal/DataAccTest.java
index 91ee6ff..771d881 100644
--- a/src/test/java/com/github/sttk/sabi/internal/DataAccTest.java
+++ b/src/test/java/com/github/sttk/sabi/internal/DataAccTest.java
@@ -3,7 +3,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.fail;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.AsyncGroup;
 import com.github.sttk.sabi.DataAcc;
 import com.github.sttk.sabi.DataConn;
@@ -37,10 +37,10 @@ static class FooDataSrc implements DataSrc {
     }
 
     @Override
-    public void setup(AsyncGroup ag) throws Exc {
+    public void setup(AsyncGroup ag) throws Err {
       if (this.willFail) {
         this.logger.add(String.format("FooDataSrc %d failed to setup", this.id));
-        throw new Exc("XXX");
+        throw new Err("XXX");
       }
       this.logger.add(String.format("FooDataSrc %d setupped", this.id));
     }
@@ -51,7 +51,7 @@ public void close() {
     }
 
     @Override
-    public DataConn createDataConn() throws Exc {
+    public DataConn createDataConn() throws Err {
       this.logger.add(String.format("FooDataSrc %d created FooDataConn", this.id));
       return new FooDataConn(this.id, this.text, this.logger);
     }
@@ -74,13 +74,13 @@ String getText() {
     }
 
     @Override
-    public void commit(AsyncGroup ag) throws Exc {
+    public void commit(AsyncGroup ag) throws Err {
       this.committed = true;
       this.logger.add(String.format("FooDataConn %d committed", this.id));
     }
 
     @Override
-    public void preCommit(AsyncGroup ag) throws Exc {
+    public void preCommit(AsyncGroup ag) throws Err {
       this.logger.add(String.format("FooDataConn %d pre committed", this.id));
     }
 
@@ -124,10 +124,10 @@ static class BarDataSrc implements DataSrc {
     }
 
     @Override
-    public void setup(AsyncGroup ag) throws Exc {
+    public void setup(AsyncGroup ag) throws Err {
       if (this.willFail) {
         this.logger.add(String.format("BarDataSrc %d failed to setup", this.id));
-        throw new Exc("XXX");
+        throw new Err("XXX");
       }
       this.logger.add(String.format("BarDataSrc %d setupped", this.id));
     }
@@ -139,7 +139,7 @@ public void close() {
     }
 
     @Override
-    public DataConn createDataConn() throws Exc {
+    public DataConn createDataConn() throws Err {
       this.logger.add(String.format("BarDataSrc %d created BarDataConn", this.id));
       return new BarDataConn(this.id, this.text, this.logger, this);
     }
@@ -165,14 +165,14 @@ void setText(String s) {
     }
 
     @Override
-    public void commit(AsyncGroup ag) throws Exc {
+    public void commit(AsyncGroup ag) throws Err {
       this.committed = true;
       this.ds.text = this.text;
       this.logger.add(String.format("BarDataConn %d committed", this.id));
     }
 
     @Override
-    public void preCommit(AsyncGroup ag) throws Exc {
+    public void preCommit(AsyncGroup ag) throws Err {
       this.logger.add(String.format("BarDataConn %d pre committed", this.id));
     }
 
@@ -206,14 +206,14 @@ public void close() {
   ///
 
   static interface SampleData {
-    String getValue() throws Exc;
+    String getValue() throws Err;
 
-    void setValue(String text) throws Exc;
+    void setValue(String text) throws Err;
   }
 
   static class SampleLogic implements Logic<SampleData> {
     @Override
-    public void run(SampleData data) throws Exc {
+    public void run(SampleData data) throws Err {
       var v = data.getValue();
       data.setValue(v);
     }
@@ -221,8 +221,8 @@ public void run(SampleData data) throws Exc {
 
   static class FailingLogic implements Logic<SampleData> {
     @Override
-    public void run(SampleData data) throws Exc {
-      throw new Exc("ZZZ");
+    public void run(SampleData data) throws Err {
+      throw new Err("ZZZ");
     }
   }
 
@@ -230,7 +230,7 @@ static interface AllLogicData extends SampleData {}
 
   static interface FooDataAcc extends DataAcc, AllLogicData {
     @Override
-    default String getValue() throws Exc {
+    default String getValue() throws Err {
       var conn = getDataConn("foo", FooDataConn.class);
       return conn.getText();
     }
@@ -238,7 +238,7 @@ default String getValue() throws Exc {
 
   static interface BarDataAcc extends DataAcc, AllLogicData {
     @Override
-    default void setValue(String text) throws Exc {
+    default void setValue(String text) throws Err {
       var conn = getDataConn("bar", BarDataConn.class);
       conn.setText(text);
     }
@@ -395,7 +395,7 @@ void test_not_run_logic_if_fail_to_setup_local_data_src() {
           data.uses("bar", new BarDataSrc(2, logger, false));
 
           Sabi.run(new SampleLogic(), data);
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToSetupLocalDataSrcs r -> {
               var e2 = r.errors().get("foo");
@@ -572,7 +572,7 @@ void test_not_run_logic_if_fail_to_setup_local_data_src() {
           data.uses("bar", new BarDataSrc(2, logger, false));
 
           Sabi.txn(new SampleLogic(), data);
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToSetupLocalDataSrcs r -> {
               var e2 = r.errors().get("foo");
@@ -601,7 +601,7 @@ void test_not_run_logic_in_txn_and_rollback() {
           data.uses("bar", new BarDataSrc(2, logger, false));
 
           Sabi.txn(new FailingLogic(), data);
-        } catch (Exc e) {
+        } catch (Err e) {
           assertThat(e.getReason()).isEqualTo("ZZZ");
         } catch (Exception e) {
           fail(e);
diff --git a/src/test/java/com/github/sttk/sabi/internal/DataConnListTest.java b/src/test/java/com/github/sttk/sabi/internal/DataConnListTest.java
index c2dcf70..61d4a11 100644
--- a/src/test/java/com/github/sttk/sabi/internal/DataConnListTest.java
+++ b/src/test/java/com/github/sttk/sabi/internal/DataConnListTest.java
@@ -2,7 +2,7 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.AsyncGroup;
 import com.github.sttk.sabi.DataConn;
 import java.util.ArrayList;
@@ -21,9 +21,9 @@ public SampleDataConn(int id, List<String> logger) {
       this.logger = logger;
     }
 
-    public void commit(AsyncGroup ag) throws Exc {}
+    public void commit(AsyncGroup ag) throws Err {}
 
-    public void preCommit(AsyncGroup ag) throws Exc {}
+    public void preCommit(AsyncGroup ag) throws Err {}
 
     public void postCommit(AsyncGroup ag) {}
 
diff --git a/src/test/java/com/github/sttk/sabi/internal/DataHubInnerTest.java b/src/test/java/com/github/sttk/sabi/internal/DataHubInnerTest.java
index acc8aa9..3227e6a 100644
--- a/src/test/java/com/github/sttk/sabi/internal/DataHubInnerTest.java
+++ b/src/test/java/com/github/sttk/sabi/internal/DataHubInnerTest.java
@@ -3,7 +3,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.fail;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.AsyncGroup;
 import com.github.sttk.sabi.DataConn;
 import com.github.sttk.sabi.DataHub;
@@ -38,10 +38,10 @@ static class SyncDataSrc implements DataSrc {
     }
 
     @Override
-    public void setup(AsyncGroup ag) throws Exc {
+    public void setup(AsyncGroup ag) throws Err {
       if (this.fail == FAIL__SETUP) {
         this.logger.add(String.format("SyncDataSrc %d failed to setup", this.id));
-        throw new Exc("XXX");
+        throw new Err("XXX");
       }
       this.logger.add(String.format("SyncDataSrc %d setupped", this.id));
     }
@@ -52,10 +52,10 @@ public void close() {
     }
 
     @Override
-    public DataConn createDataConn() throws Exc {
+    public DataConn createDataConn() throws Err {
       if (this.fail == FAIL__CREATE_DATA_CONN) {
         this.logger.add(String.format("SyncDataSrc %d failed to create a DataConn", this.id));
-        throw new Exc("xxx");
+        throw new Err("xxx");
       }
       this.logger.add(String.format("SyncDataSrc %d created DataConn", this.id));
       var conn = new SyncDataConn(this.id, this.fail, this.logger);
@@ -75,7 +75,7 @@ static class AsyncDataSrc implements DataSrc {
     }
 
     @Override
-    public void setup(AsyncGroup ag) throws Exc {
+    public void setup(AsyncGroup ag) throws Err {
       ag.add(
           () -> {
             try {
@@ -84,7 +84,7 @@ public void setup(AsyncGroup ag) throws Exc {
             }
             if (this.fail == FAIL__SETUP) {
               this.logger.add(String.format("AsyncDataSrc %d failed to setup", this.id));
-              throw new Exc("YYY");
+              throw new Err("YYY");
             }
             this.logger.add(String.format("AsyncDataSrc %d setupped", this.id));
           });
@@ -96,10 +96,10 @@ public void close() {
     }
 
     @Override
-    public DataConn createDataConn() throws Exc {
+    public DataConn createDataConn() throws Err {
       if (this.fail == FAIL__CREATE_DATA_CONN) {
         this.logger.add(String.format("AsyncDataSrc %d failed to create a DataConn", this.id));
-        throw new Exc("yyy");
+        throw new Err("yyy");
       }
       this.logger.add(String.format("AsyncDataSrc %d created DataConn", this.id));
       var conn = new AsyncDataConn(this.id, this.fail, this.logger);
@@ -120,20 +120,20 @@ static class SyncDataConn implements DataConn {
     }
 
     @Override
-    public void commit(AsyncGroup ag) throws Exc {
+    public void commit(AsyncGroup ag) throws Err {
       if (this.fail == FAIL__COMMIT) {
         this.logger.add(String.format("SyncDataConn %d failed to commit", this.id));
-        throw new Exc("ZZZ");
+        throw new Err("ZZZ");
       }
       this.committed = true;
       this.logger.add(String.format("SyncDataConn %d committed", this.id));
     }
 
     @Override
-    public void preCommit(AsyncGroup ag) throws Exc {
+    public void preCommit(AsyncGroup ag) throws Err {
       if (this.fail == FAIL__PRE_COMMIT) {
         this.logger.add(String.format("SyncDataConn %d failed to pre commit", this.id));
-        throw new Exc("zzz");
+        throw new Err("zzz");
       }
       this.logger.add(String.format("SyncDataConn %d pre committed", this.id));
     }
@@ -177,20 +177,20 @@ static class AsyncDataConn implements DataConn {
     }
 
     @Override
-    public void commit(AsyncGroup ag) throws Exc {
+    public void commit(AsyncGroup ag) throws Err {
       if (this.fail == FAIL__COMMIT) {
         this.logger.add(String.format("AsyncDataConn %d failed to commit", this.id));
-        throw new Exc("VVV");
+        throw new Err("VVV");
       }
       this.committed = true;
       this.logger.add(String.format("AsyncDataConn %d committed", this.id));
     }
 
     @Override
-    public void preCommit(AsyncGroup ag) throws Exc {
+    public void preCommit(AsyncGroup ag) throws Err {
       if (this.fail == FAIL__PRE_COMMIT) {
         this.logger.add(String.format("AsyncDataConn %d failed to pre commit", this.id));
-        throw new Exc("vvv");
+        throw new Err("vvv");
       }
       this.logger.add(String.format("AsyncDataConn %d pre committed", this.id));
     }
@@ -310,7 +310,7 @@ void fail_to_setup() {
       try (var ac = DataHubInner.setupGlobals()) {
         suppressWarnings_unused(ac);
         fail();
-      } catch (Exc e) {
+      } catch (Err e) {
         switch (e.getReason()) {
           case DataHub.FailToSetupGlobalDataSrcs r -> {
             assertThat(r.errors()).hasSize(2);
@@ -833,7 +833,7 @@ void begin_and_end_but_fail_sync() {
 
         try {
           hub.begin();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToSetupLocalDataSrcs rsn -> {
               assertThat(rsn.errors()).hasSize(1);
@@ -908,7 +908,7 @@ void begin_and_end_but_fail_async() {
 
         try {
           hub.begin();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToSetupLocalDataSrcs rsn -> {
               assertThat(rsn.errors()).hasSize(1);
@@ -1073,7 +1073,7 @@ void fail_to_cast_new_data_conn() {
         try {
           hub.getDataConn("foo", SyncDataConn.class);
           fail();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToCastDataConn rsn -> {
               assertThat(rsn.name()).isEqualTo("foo");
@@ -1089,7 +1089,7 @@ void fail_to_cast_new_data_conn() {
         try {
           hub.getDataConn("bar", AsyncDataConn.class);
           fail();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToCastDataConn rsn -> {
               assertThat(rsn.name()).isEqualTo("bar");
@@ -1146,7 +1146,7 @@ void fail_to_cast_reused_data_conn() {
         try {
           hub.getDataConn("foo", SyncDataConn.class);
           fail();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToCastDataConn rsn -> {
               assertThat(rsn.name()).isEqualTo("foo");
@@ -1162,7 +1162,7 @@ void fail_to_cast_reused_data_conn() {
         try {
           hub.getDataConn("bar", AsyncDataConn.class);
           fail();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToCastDataConn rsn -> {
               assertThat(rsn.name()).isEqualTo("bar");
@@ -1216,7 +1216,7 @@ void fail_to_create_data_conn() {
         try {
           hub.getDataConn("bar", AsyncDataConn.class);
           fail();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToCreateDataConn rsn -> {
               assertThat(rsn.name()).isEqualTo("bar");
@@ -1266,7 +1266,7 @@ void fail_to_create_data_conn_because_of_no_data_src() {
         try {
           hub.getDataConn("baz", SyncDataConn.class);
           fail();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.NoDataSrcToCreateDataConn rsn -> {
               assertThat(rsn.name()).isEqualTo("baz");
@@ -1282,7 +1282,7 @@ void fail_to_create_data_conn_because_of_no_data_src() {
         try {
           hub.getDataConn("qux", AsyncDataConn.class);
           fail();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.NoDataSrcToCreateDataConn rsn -> {
               assertThat(rsn.name()).isEqualTo("qux");
@@ -1377,7 +1377,7 @@ void commit_but_fail_global_sync() {
 
         try {
           hub.commit();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToCommitDataConn rsn -> {
               assertThat(rsn.errors()).hasSize(1);
@@ -1453,7 +1453,7 @@ void commit_but_fail_global_async() {
 
         try {
           hub.commit();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToCommitDataConn rsn -> {
               assertThat(rsn.errors()).hasSize(1);
@@ -1528,7 +1528,7 @@ void commit_but_fail_local_sync() {
 
         try {
           hub.commit();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToCommitDataConn rsn -> {
               assertThat(rsn.errors()).hasSize(1);
@@ -1606,7 +1606,7 @@ void commit_but_fail_local_async() {
 
         try {
           hub.commit();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToCommitDataConn rsn -> {
               assertThat(rsn.errors()).hasSize(1);
@@ -1683,7 +1683,7 @@ void pre_commit_but_fail_global_sync() {
 
         try {
           hub.commit();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToPreCommitDataConn rsn -> {
               assertThat(rsn.errors()).hasSize(1);
@@ -1755,7 +1755,7 @@ void pre_commit_but_fail_global_async() {
 
         try {
           hub.commit();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToPreCommitDataConn rsn -> {
               assertThat(rsn.errors()).hasSize(1);
@@ -1827,7 +1827,7 @@ void pre_commit_but_fail_local_sync() {
 
         try {
           hub.commit();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToPreCommitDataConn rsn -> {
               assertThat(rsn.errors()).hasSize(1);
@@ -1901,7 +1901,7 @@ void pre_commit_but_fail_local_async() {
 
         try {
           hub.commit();
-        } catch (Exc e) {
+        } catch (Err e) {
           switch (e.getReason()) {
             case DataHub.FailToPreCommitDataConn rsn -> {
               assertThat(rsn.errors()).hasSize(1);
diff --git a/src/test/java/com/github/sttk/sabi/internal/DataSrcListTest.java b/src/test/java/com/github/sttk/sabi/internal/DataSrcListTest.java
index d37bb71..da381b7 100644
--- a/src/test/java/com/github/sttk/sabi/internal/DataSrcListTest.java
+++ b/src/test/java/com/github/sttk/sabi/internal/DataSrcListTest.java
@@ -3,7 +3,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.fail;
 
-import com.github.sttk.errs.Exc;
+import com.github.sttk.errs.Err;
 import com.github.sttk.sabi.AsyncGroup;
 import com.github.sttk.sabi.DataConn;
 import com.github.sttk.sabi.DataSrc;
@@ -27,10 +27,10 @@ static class SyncDataSrc implements DataSrc {
     }
 
     @Override
-    public void setup(AsyncGroup ag) throws Exc {
+    public void setup(AsyncGroup ag) throws Err {
       if (this.willFail) {
         logger.add(String.format("SyncDataSrc %d failed to setup", this.id));
-        throw new Exc("XXX");
+        throw new Err("XXX");
       }
       logger.add(String.format("SyncDataSrc %d setupped", this.id));
     }
@@ -41,7 +41,7 @@ public void close() {
     }
 
     @Override
-    public DataConn createDataConn() throws Exc {
+    public DataConn createDataConn() throws Err {
       logger.add(String.format("SyncDataSrc %d created DataConn", this.id));
       var conn = new SyncDataConn();
       return conn;
@@ -60,7 +60,7 @@ static class AsyncDataSrc implements DataSrc {
     }
 
     @Override
-    public void setup(AsyncGroup ag) throws Exc {
+    public void setup(AsyncGroup ag) throws Err {
       ag.add(
           () -> {
             try {
@@ -69,7 +69,7 @@ public void setup(AsyncGroup ag) throws Exc {
             }
             if (this.willFail) {
               logger.add(String.format("AsyncDataSrc %d failed to setup", this.id));
-              throw new Exc("XXX");
+              throw new Err("XXX");
             }
             logger.add(String.format("AsyncDataSrc %d setupped", this.id));
           });
@@ -81,7 +81,7 @@ public void close() {
     }
 
     @Override
-    public DataConn createDataConn() throws Exc {
+    public DataConn createDataConn() throws Err {
       logger.add(String.format("AsyncDataSrc %d created DataConn", this.id));
       var conn = new AsyncDataConn();
       return conn;
@@ -90,10 +90,10 @@ public DataConn createDataConn() throws Exc {
 
   static class SyncDataConn implements DataConn {
     @Override
-    public void commit(AsyncGroup ag) throws Exc {}
+    public void commit(AsyncGroup ag) throws Err {}
 
     @Override
-    public void preCommit(AsyncGroup ag) throws Exc {}
+    public void preCommit(AsyncGroup ag) throws Err {}
 
     @Override
     public void postCommit(AsyncGroup ag) {}
@@ -115,10 +115,10 @@ public void close() {}
 
   static class AsyncDataConn implements DataConn {
     @Override
-    public void commit(AsyncGroup ag) throws Exc {}
+    public void commit(AsyncGroup ag) throws Err {}
 
     @Override
-    public void preCommit(AsyncGroup ag) throws Exc {}
+    public void preCommit(AsyncGroup ag) throws Err {}
 
     @Override
     public void postCommit(AsyncGroup ag) {}
@@ -911,7 +911,7 @@ void test_setupAndCreateDataConnAndClose() {
     try {
       var conn = ptr.ds.createDataConn();
       assertThat(conn).isNotNull();
-    } catch (Exc e) {
+    } catch (Err e) {
       fail(e);
     }
 
@@ -919,7 +919,7 @@ void test_setupAndCreateDataConnAndClose() {
     try {
       var conn = ptr.ds.createDataConn();
       assertThat(conn).isNotNull();
-    } catch (Exc e) {
+    } catch (Err e) {
       fail(e);
     }
 
@@ -972,11 +972,11 @@ void test_failToSetupAsyncAndClose() {
     var dsSync = new SyncDataSrc(2, logger, false);
     dsList.addDataSrc("bar", dsSync);
 
-    var excMap = dsList.setupDataSrcs();
-    assertThat(excMap).hasSize(1);
+    var errMap = dsList.setupDataSrcs();
+    assertThat(errMap).hasSize(1);
 
-    var exc = excMap.get("foo");
-    assertThat(exc.getReason()).isEqualTo("XXX");
+    var err = errMap.get("foo");
+    assertThat(err.getReason()).isEqualTo("XXX");
 
     dsList.closeDataSrcs();
 
@@ -989,8 +989,8 @@ void test_failToSetupAsyncAndClose() {
   void test_noDataSrc() {
     var dsList = new DataSrcList(false);
 
-    var excMap = dsList.setupDataSrcs();
-    assertThat(excMap).hasSize(0);
+    var errMap = dsList.setupDataSrcs();
+    assertThat(errMap).hasSize(0);
 
     dsList.closeDataSrcs();