diff --git a/bundles/sirix-core/src/main/java/io/sirix/access/trx/TransactionGroupCommitter.java b/bundles/sirix-core/src/main/java/io/sirix/access/trx/TransactionGroupCommitter.java
deleted file mode 100644
index e665bcf4c..000000000
--- a/bundles/sirix-core/src/main/java/io/sirix/access/trx/TransactionGroupCommitter.java
+++ /dev/null
@@ -1,16 +0,0 @@
-package io.sirix.access.trx;
-
-import io.sirix.api.NodeTrx;
-
-import java.util.Set;
-
-public final class TransactionGroupCommitter {
-
-  private final Set<NodeTrx> transactions;
-
-  public TransactionGroupCommitter(Set<NodeTrx> transactions) {
-    this.transactions = transactions;
-  }
-
-
-}
diff --git a/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/AbstractResourceSession.java b/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/AbstractResourceSession.java
index 9641f2de5..99aabaed0 100644
--- a/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/AbstractResourceSession.java
+++ b/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/AbstractResourceSession.java
@@ -136,6 +136,11 @@ public abstract class AbstractResourceSession<R extends NodeReadOnlyTrx & NodeCu
    */
   private final PageTrxFactory pageTrxFactory;
 
+  /**
+   * ID Generation exception message for duplicate ID.
+   */
+  private final String ID_GENERATION_EXCEPTION = "ID generation is bogus because of duplicate ID.";
+
   /**
    * Creates a new instance of this class.
    *
@@ -347,7 +352,7 @@ public synchronized R beginNodeReadOnlyTrx(@NonNegative final int revision) {
 
     // Remember reader for debugging and safe close.
     if (nodeTrxMap.put(reader.getId(), reader) != null) {
-      throw new SirixUsageException("ID generation is bogus because of duplicate ID.");
+      throw new SirixUsageException(ID_GENERATION_EXCEPTION);
     }
 
     return reader;
@@ -450,7 +455,7 @@ public synchronized W beginNodeTrx(final @NonNegative int maxNodeCount, final @N
 
     // Remember node transaction for debugging and safe close.
     if (nodeTrxMap.put(nodeTrxId, (R) wtx) != null || nodePageTrxMap.put(nodeTrxId, pageWtx) != null) {
-      throw new SirixThreadedException("ID generation is bogus because of duplicate ID.");
+      throw new SirixThreadedException(ID_GENERATION_EXCEPTION);
     }
 
     return wtx;
@@ -721,7 +726,7 @@ public PageReadOnlyTrx beginPageReadOnlyTrx(final @NonNegative int revision) {
 
     // Remember page transaction for debugging and safe close.
     if (pageTrxMap.put(currentPageTrxID, pageReadTrx) != null) {
-      throw new SirixThreadedException("ID generation is bogus because of duplicate ID.");
+      throw new SirixThreadedException(ID_GENERATION_EXCEPTION);
     }
 
     return pageReadTrx;
@@ -748,7 +753,7 @@ public synchronized PageTrx beginPageTrx(final @NonNegative int revision) {
 
     // Remember page transaction for debugging and safe close.
     if (pageTrxMap.put(currentPageTrxID, pageTrx) != null) {
-      throw new SirixThreadedException("ID generation is bogus because of duplicate ID.");
+      throw new SirixThreadedException(ID_GENERATION_EXCEPTION);
     }
 
     return pageTrx;
diff --git a/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/json/JsonNodeReadOnlyTrxImpl.java b/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/json/JsonNodeReadOnlyTrxImpl.java
index 3d1bb21cc..066e2c507 100644
--- a/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/json/JsonNodeReadOnlyTrxImpl.java
+++ b/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/json/JsonNodeReadOnlyTrxImpl.java
@@ -57,6 +57,11 @@ public final class JsonNodeReadOnlyTrxImpl
     super(trxId, pageReadTransaction, documentNode, resourceManager, new ItemListImpl());
   }
 
+  private final String INSERT = "insert";
+  private final String UPDATE = "update";
+  private final String DELETE = "delete";
+  private final String REPLACE = "replace";
+
   @Override
   public boolean hasLastChild() {
     assertNotClosed();
@@ -103,10 +108,10 @@ private Consumer<JsonElement> serializeJsonFragmentIfNeeded(final List<JsonObjec
       final var diffObject = diff.getAsJsonObject();
 
       final JsonObject diffTupleObject;
-      if (diffObject.has("insert")) {
-        diffTupleObject = diffObject.getAsJsonObject("insert");
-      } else if (diffObject.has("replace")) {
-        diffTupleObject = diffObject.getAsJsonObject("replace");
+      if (diffObject.has(INSERT)) {
+        diffTupleObject = diffObject.getAsJsonObject(INSERT);
+      } else if (diffObject.has(REPLACE)) {
+        diffTupleObject = diffObject.getAsJsonObject(REPLACE);
       } else {
         diffTupleObject = null;
       }
@@ -146,14 +151,14 @@ public List<JsonObject> getUpdateOperationsInSubtreeOfNode(final SirixDeweyID ro
 
   private Comparator<JsonObject> sortByDeweyID() {
     return Comparator.comparing(updateOperation -> {
-      if (updateOperation.has("insert")) {
-        return getDeweyID(updateOperation, "insert");
-      } else if (updateOperation.has("delete")) {
-        return getDeweyID(updateOperation, "delete");
-      } else if (updateOperation.has("update")) {
-        return getDeweyID(updateOperation, "update");
-      } else if (updateOperation.has("replace")) {
-        return getDeweyID(updateOperation, "replace");
+      if (updateOperation.has(INSERT)) {
+        return getDeweyID(updateOperation, INSERT);
+      } else if (updateOperation.has(DELETE)) {
+        return getDeweyID(updateOperation, DELETE);
+      } else if (updateOperation.has(UPDATE)) {
+        return getDeweyID(updateOperation, UPDATE);
+      } else if (updateOperation.has(REPLACE)) {
+        return getDeweyID(updateOperation, REPLACE);
       }
       throw new IllegalStateException(updateOperation + " not known.");
     });
@@ -161,14 +166,14 @@ private Comparator<JsonObject> sortByDeweyID() {
 
   private Predicate<JsonObject> filterAncestorOperations(SirixDeweyID rootDeweyId, long maxDepth) {
     return updateOperation -> {
-      if (updateOperation.has("insert")) {
-        return isDescendatOrSelfOf(rootDeweyId, updateOperation, "insert", maxDepth);
-      } else if (updateOperation.has("delete")) {
-        return isDescendatOrSelfOf(rootDeweyId, updateOperation, "delete", maxDepth);
-      } else if (updateOperation.has("update")) {
-        return isDescendatOrSelfOf(rootDeweyId, updateOperation, "update", maxDepth);
-      } else if (updateOperation.has("replace")) {
-        return isDescendatOrSelfOf(rootDeweyId, updateOperation, "replace", maxDepth);
+      if (updateOperation.has(INSERT)) {
+        return isDescendatOrSelfOf(rootDeweyId, updateOperation, INSERT, maxDepth);
+      } else if (updateOperation.has(DELETE)) {
+        return isDescendatOrSelfOf(rootDeweyId, updateOperation, DELETE, maxDepth);
+      } else if (updateOperation.has(UPDATE)) {
+        return isDescendatOrSelfOf(rootDeweyId, updateOperation, UPDATE, maxDepth);
+      } else if (updateOperation.has(REPLACE)) {
+        return isDescendatOrSelfOf(rootDeweyId, updateOperation, REPLACE, maxDepth);
       } else {
         throw new IllegalStateException(updateOperation + " not known.");
       }
diff --git a/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/json/JsonNodeTrxImpl.java b/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/json/JsonNodeTrxImpl.java
index e43e4c3cf..5363b95ea 100644
--- a/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/json/JsonNodeTrxImpl.java
+++ b/bundles/sirix-core/src/main/java/io/sirix/access/trx/node/json/JsonNodeTrxImpl.java
@@ -378,9 +378,6 @@ private JsonNodeTrx insertSubtree(final JsonReader reader, final InsertPosition
           commit();
         }
 
-        //      for (final long unused : new DescendantAxis(nodeReadOnlyTrx)) {
-        //        System.out.println(nodeReadOnlyTrx.getDeweyID());
-        //      }
       } catch (final IOException e) {
         throw new UncheckedIOException(e);
       }
@@ -553,9 +550,6 @@ private JsonNodeTrx insertSubtree(final Item item, final InsertPosition insertio
         commit();
       }
 
-      //      for (final long unused : new DescendantAxis(nodeReadOnlyTrx)) {
-      //        System.out.println(nodeReadOnlyTrx.getDeweyID());
-      //      }
     });
     return this;
   }