diff --git a/src/main/java/com/ericsson/gerrit/plugins/highavailability/forwarder/ForwardedIndexChangeHandler.java b/src/main/java/com/ericsson/gerrit/plugins/highavailability/forwarder/ForwardedIndexChangeHandler.java
index f7ea962..3a0e686 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/highavailability/forwarder/ForwardedIndexChangeHandler.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/highavailability/forwarder/ForwardedIndexChangeHandler.java
@@ -18,6 +18,7 @@
 import com.ericsson.gerrit.plugins.highavailability.Configuration.Index;
 import com.ericsson.gerrit.plugins.highavailability.index.ChangeChecker;
 import com.ericsson.gerrit.plugins.highavailability.index.ChangeCheckerImpl;
+import com.ericsson.gerrit.plugins.highavailability.index.ChangeDb;
 import com.ericsson.gerrit.plugins.highavailability.index.ForwardedIndexExecutor;
 import com.google.common.base.Splitter;
 import com.google.gerrit.reviewdb.client.Change;
@@ -29,7 +30,6 @@
 import com.google.gerrit.server.util.ManualRequestContext;
 import com.google.gerrit.server.util.OneOffRequestContext;
 import com.google.gwtorm.server.OrmException;
-import com.google.gwtorm.server.SchemaFactory;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import java.io.IOException;
@@ -46,7 +46,7 @@
 @Singleton
 public class ForwardedIndexChangeHandler extends ForwardedIndexingHandler<String> {
   private final ChangeIndexer indexer;
-  private final SchemaFactory<ReviewDb> schemaFactory;
+  private final ChangeDb changeDb;
   private final ScheduledExecutorService indexExecutor;
   private final OneOffRequestContext oneOffCtx;
   private final int retryInterval;
@@ -56,7 +56,7 @@
   @Inject
   ForwardedIndexChangeHandler(
       ChangeIndexer indexer,
-      SchemaFactory<ReviewDb> schemaFactory,
+      ChangeDb changeDb,
       ChangeFinder changeFinder,
       Configuration config,
       @ForwardedIndexExecutor ScheduledExecutorService indexExecutor,
@@ -64,7 +64,7 @@
       ChangeCheckerImpl.Factory changeCheckerFactory) {
     super(config.index());
     this.indexer = indexer;
-    this.schemaFactory = schemaFactory;
+    this.changeDb = changeDb;
     this.indexExecutor = indexExecutor;
     this.oneOffCtx = oneOffCtx;
     this.changeCheckerFactory = changeCheckerFactory;
@@ -82,13 +82,12 @@
 
   private void doIndex(String id, Optional<IndexEvent> indexEvent, int retryCount)
       throws IOException, OrmException {
-    try (ReviewDb db = schemaFactory.open()) {
+    try {
       ChangeChecker checker = changeCheckerFactory.create(id);
       Optional<ChangeNotes> changeNotes = checker.getChangeNotes();
       if (changeNotes.isPresent()) {
         ChangeNotes notes = changeNotes.get();
-        notes.reload();
-        indexer.index(db, notes.getChange());
+        reindex(notes);
 
         if (checker.isChangeUpToDate(indexEvent)) {
           if (retryCount > 0) {
@@ -122,6 +121,13 @@
     }
   }
 
+  private void reindex(ChangeNotes notes) throws IOException, OrmException {
+    try (ReviewDb db = changeDb.open()) {
+      notes.reload();
+      indexer.index(db, notes.getChange());
+    }
+  }
+
   private void rescheduleIndex(String id, Optional<IndexEvent> indexEvent, int retryCount) {
     if (retryCount > maxTries) {
       log.error(
diff --git a/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeCheckerImpl.java b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeCheckerImpl.java
index 7b662dd..88aa5ca 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeCheckerImpl.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeCheckerImpl.java
@@ -25,7 +25,6 @@
 import com.google.gerrit.server.util.ManualRequestContext;
 import com.google.gerrit.server.util.OneOffRequestContext;
 import com.google.gwtorm.server.OrmException;
-import com.google.gwtorm.server.SchemaFactory;
 import com.google.inject.Inject;
 import com.google.inject.assistedinject.Assisted;
 import java.io.IOException;
@@ -41,7 +40,7 @@
   private static final Logger log = LoggerFactory.getLogger(ChangeCheckerImpl.class);
   private final GitRepositoryManager gitRepoMgr;
   private final CommentsUtil commentsUtil;
-  private final SchemaFactory<ReviewDb> schemaFactory;
+  private final ChangeDb changeDb;
   private final OneOffRequestContext oneOffReqCtx;
   private final String changeId;
   private final ChangeFinder changeFinder;
@@ -56,14 +55,14 @@
   public ChangeCheckerImpl(
       GitRepositoryManager gitRepoMgr,
       CommentsUtil commentsUtil,
-      SchemaFactory<ReviewDb> schemaFactory,
+      ChangeDb changeDb,
       ChangeFinder changeFinder,
       OneOffRequestContext oneOffReqCtx,
       @Assisted String changeId) {
     this.changeFinder = changeFinder;
     this.gitRepoMgr = gitRepoMgr;
     this.commentsUtil = commentsUtil;
-    this.schemaFactory = schemaFactory;
+    this.changeDb = changeDb;
     this.oneOffReqCtx = oneOffReqCtx;
     this.changeId = changeId;
   }
@@ -80,21 +79,6 @@
             });
   }
 
-  private String getBranchTargetSha() {
-    try (Repository repo = gitRepoMgr.openRepository(changeNotes.get().getProjectName())) {
-      String refName = changeNotes.get().getChange().getDest().get();
-      Ref ref = repo.findRef(refName);
-      if (ref == null) {
-        log.warn("Unable to find target ref {} for change {}", refName, changeId);
-        return null;
-      }
-      return ref.getTarget().getObjectId().getName();
-    } catch (IOException e) {
-      log.warn("Unable to resolve target branch SHA for change {}", changeId, e);
-      return null;
-    }
-  }
-
   @Override
   public Optional<ChangeNotes> getChangeNotes() throws OrmException {
     try (ManualRequestContext ctx = oneOffReqCtx.open()) {
@@ -113,13 +97,16 @@
       return false;
     }
 
-    String targetSha = getBranchTargetSha();
+    if (indexEvent.isPresent() && indexEvent.get().targetSha == null) {
+      return indexEvent.map(e -> (computedChangeTs.get() >= e.eventCreatedOn)).orElse(true);
+    }
+
     return indexEvent
         .map(
             e ->
                 (computedChangeTs.get() > e.eventCreatedOn)
                     || (computedChangeTs.get() == e.eventCreatedOn)
-                        && (Objects.equals(targetSha, e.targetSha)))
+                        && (Objects.equals(getBranchTargetSha(), e.targetSha)))
         .orElse(true);
   }
 
@@ -146,8 +133,23 @@
     }
   }
 
+  private String getBranchTargetSha() {
+    try (Repository repo = gitRepoMgr.openRepository(changeNotes.get().getProjectName())) {
+      String refName = changeNotes.get().getChange().getDest().get();
+      Ref ref = repo.exactRef(refName);
+      if (ref == null) {
+        log.warn("Unable to find target ref {} for change {}", refName, changeId);
+        return null;
+      }
+      return ref.getTarget().getObjectId().getName();
+    } catch (IOException e) {
+      log.warn("Unable to resolve target branch SHA for change {}", changeId, e);
+      return null;
+    }
+  }
+
   private Optional<Long> computeLastChangeTs() throws OrmException {
-    try (ReviewDb db = schemaFactory.open()) {
+    try (ReviewDb db = changeDb.open()) {
       return getChangeNotes().map(notes -> getTsFromChangeAndDraftComments(db, notes));
     }
   }
diff --git a/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeDb.java b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeDb.java
new file mode 100644
index 0000000..bef5363
--- /dev/null
+++ b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/ChangeDb.java
@@ -0,0 +1,38 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.ericsson.gerrit.plugins.highavailability.index;
+
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.notedb.NotesMigration;
+import com.google.gwtorm.server.OrmException;
+import com.google.gwtorm.server.SchemaFactory;
+import com.google.inject.Inject;
+
+public class ChangeDb {
+  private static final DisabledReviewDb disabledReviewDb = new DisabledReviewDb();
+
+  private final NotesMigration migration;
+  private final SchemaFactory<ReviewDb> schemaFactory;
+
+  @Inject
+  public ChangeDb(NotesMigration migration, SchemaFactory<ReviewDb> schemaFactory) {
+    this.migration = migration;
+    this.schemaFactory = schemaFactory;
+  }
+
+  public ReviewDb open() throws OrmException {
+    return migration.readChanges() ? disabledReviewDb : schemaFactory.open();
+  }
+}
diff --git a/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/DisabledReviewDb.java b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/DisabledReviewDb.java
new file mode 100644
index 0000000..192ee8c
--- /dev/null
+++ b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/DisabledReviewDb.java
@@ -0,0 +1,244 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.ericsson.gerrit.plugins.highavailability.index;
+
+import com.google.common.util.concurrent.CheckedFuture;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.Change.Id;
+import com.google.gerrit.reviewdb.server.AccountGroupAccess;
+import com.google.gerrit.reviewdb.server.AccountGroupByIdAccess;
+import com.google.gerrit.reviewdb.server.AccountGroupByIdAudAccess;
+import com.google.gerrit.reviewdb.server.AccountGroupMemberAccess;
+import com.google.gerrit.reviewdb.server.AccountGroupMemberAuditAccess;
+import com.google.gerrit.reviewdb.server.AccountGroupNameAccess;
+import com.google.gerrit.reviewdb.server.ChangeAccess;
+import com.google.gerrit.reviewdb.server.ChangeMessageAccess;
+import com.google.gerrit.reviewdb.server.PatchLineCommentAccess;
+import com.google.gerrit.reviewdb.server.PatchSetAccess;
+import com.google.gerrit.reviewdb.server.PatchSetApprovalAccess;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.reviewdb.server.SchemaVersionAccess;
+import com.google.gerrit.reviewdb.server.SystemConfigAccess;
+import com.google.gwtorm.server.Access;
+import com.google.gwtorm.server.AtomicUpdate;
+import com.google.gwtorm.server.OrmException;
+import com.google.gwtorm.server.ResultSet;
+import com.google.gwtorm.server.StatementExecutor;
+import java.util.Map;
+
+/** ReviewDb that is disabled. */
+@SuppressWarnings("deprecation")
+public class DisabledReviewDb implements ReviewDb {
+  public static class Disabled extends RuntimeException {
+    private static final long serialVersionUID = 1L;
+
+    private Disabled() {
+      super("ReviewDb is disabled for changes");
+    }
+  }
+
+  public static class DisabledChangeAccess implements ChangeAccess {
+
+    @Override
+    public String getRelationName() {
+      throw new Disabled();
+    }
+
+    @Override
+    public int getRelationID() {
+      throw new Disabled();
+    }
+
+    @Override
+    public ResultSet<Change> iterateAllEntities() throws OrmException {
+      throw new Disabled();
+    }
+
+    @Override
+    public Id primaryKey(Change entity) {
+      throw new Disabled();
+    }
+
+    @Override
+    public Map<Id, Change> toMap(Iterable<Change> c) {
+      throw new Disabled();
+    }
+
+    @Override
+    public CheckedFuture<Change, OrmException> getAsync(Id key) {
+      throw new Disabled();
+    }
+
+    @Override
+    public ResultSet<Change> get(Iterable<Id> keys) throws OrmException {
+      throw new Disabled();
+    }
+
+    @Override
+    public void insert(Iterable<Change> instances) throws OrmException {
+      throw new Disabled();
+    }
+
+    @Override
+    public void update(Iterable<Change> instances) throws OrmException {
+      throw new Disabled();
+    }
+
+    @Override
+    public void upsert(Iterable<Change> instances) throws OrmException {
+      throw new Disabled();
+    }
+
+    @Override
+    public void deleteKeys(Iterable<Id> keys) throws OrmException {
+      throw new Disabled();
+    }
+
+    @Override
+    public void delete(Iterable<Change> instances) throws OrmException {
+      throw new Disabled();
+    }
+
+    @Override
+    public void beginTransaction(Id key) throws OrmException {
+      throw new Disabled();
+    }
+
+    @Override
+    public Change atomicUpdate(Id key, AtomicUpdate<Change> update) throws OrmException {
+      throw new Disabled();
+    }
+
+    @Override
+    public Change get(Id id) throws OrmException {
+      return null;
+    }
+
+    @Override
+    public ResultSet<Change> all() throws OrmException {
+      return null;
+    }
+  }
+
+  @Override
+  public void close() {
+    // Do nothing.
+  }
+
+  @Override
+  public void commit() {
+    throw new Disabled();
+  }
+
+  @Override
+  public void rollback() {
+    throw new Disabled();
+  }
+
+  @Override
+  public void updateSchema(StatementExecutor e) {
+    throw new Disabled();
+  }
+
+  @Override
+  public void pruneSchema(StatementExecutor e) {
+    throw new Disabled();
+  }
+
+  @Override
+  public Access<?, ?>[] allRelations() {
+    throw new Disabled();
+  }
+
+  @Override
+  public SchemaVersionAccess schemaVersion() {
+    throw new Disabled();
+  }
+
+  @Override
+  public SystemConfigAccess systemConfig() {
+    throw new Disabled();
+  }
+
+  @Override
+  public AccountGroupAccess accountGroups() {
+    throw new Disabled();
+  }
+
+  @Override
+  public AccountGroupNameAccess accountGroupNames() {
+    throw new Disabled();
+  }
+
+  @Override
+  public AccountGroupMemberAccess accountGroupMembers() {
+    throw new Disabled();
+  }
+
+  @Override
+  public AccountGroupMemberAuditAccess accountGroupMembersAudit() {
+    throw new Disabled();
+  }
+
+  @Override
+  public ChangeAccess changes() {
+    return new DisabledChangeAccess();
+  }
+
+  @Override
+  public PatchSetApprovalAccess patchSetApprovals() {
+    throw new Disabled();
+  }
+
+  @Override
+  public ChangeMessageAccess changeMessages() {
+    throw new Disabled();
+  }
+
+  @Override
+  public PatchSetAccess patchSets() {
+    throw new Disabled();
+  }
+
+  @Override
+  public PatchLineCommentAccess patchComments() {
+    throw new Disabled();
+  }
+
+  @Override
+  public AccountGroupByIdAccess accountGroupById() {
+    throw new Disabled();
+  }
+
+  @Override
+  public AccountGroupByIdAudAccess accountGroupByIdAud() {
+    throw new Disabled();
+  }
+
+  @Override
+  public int nextAccountId() {
+    throw new Disabled();
+  }
+
+  @Override
+  public int nextAccountGroupId() {
+    throw new Disabled();
+  }
+
+  @Override
+  public int nextChangeId() {
+    throw new Disabled();
+  }
+}
diff --git a/src/test/java/com/ericsson/gerrit/plugins/highavailability/forwarder/ForwardedIndexChangeHandlerTest.java b/src/test/java/com/ericsson/gerrit/plugins/highavailability/forwarder/ForwardedIndexChangeHandlerTest.java
index 9ec0d3c..35aee31 100644
--- a/src/test/java/com/ericsson/gerrit/plugins/highavailability/forwarder/ForwardedIndexChangeHandlerTest.java
+++ b/src/test/java/com/ericsson/gerrit/plugins/highavailability/forwarder/ForwardedIndexChangeHandlerTest.java
@@ -27,6 +27,7 @@
 import com.ericsson.gerrit.plugins.highavailability.forwarder.ForwardedIndexingHandler.Operation;
 import com.ericsson.gerrit.plugins.highavailability.index.ChangeChecker;
 import com.ericsson.gerrit.plugins.highavailability.index.ChangeCheckerImpl;
+import com.ericsson.gerrit.plugins.highavailability.index.ChangeDb;
 import com.google.gerrit.common.TimeUtil;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.server.ReviewDb;
@@ -34,10 +35,8 @@
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.index.change.ChangeIndexer;
 import com.google.gerrit.server.notedb.ChangeNotes;
-import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gerrit.server.util.OneOffRequestContext;
 import com.google.gwtorm.server.OrmException;
-import com.google.gwtorm.server.SchemaFactory;
 import java.io.IOException;
 import java.util.Optional;
 import java.util.concurrent.ScheduledExecutorService;
@@ -67,7 +66,7 @@
 
   @Rule public ExpectedException exception = ExpectedException.none();
   @Mock private ChangeIndexer indexerMock;
-  @Mock private SchemaFactory<ReviewDb> schemaFactoryMock;
+  @Mock private ChangeDb changeDbMock;
   @Mock private ReviewDb dbMock;
   @Mock private ChangeNotes changeNotes;
   @Mock private Configuration configMock;
@@ -85,7 +84,7 @@
 
   @Before
   public void setUp() throws Exception {
-    when(schemaFactoryMock.open()).thenReturn(dbMock);
+    when(changeDbMock.open()).thenReturn(dbMock);
     id = new Change.Id(TEST_CHANGE_NUMBER);
     change = new Change(null, id, null, null, TimeUtil.nowTs());
     when(changeNotes.getChange()).thenReturn(change);
@@ -95,7 +94,7 @@
     handler =
         new ForwardedIndexChangeHandler(
             indexerMock,
-            schemaFactoryMock,
+            changeDbMock,
             changeFinderMock,
             configMock,
             indexExecutorMock,
@@ -138,21 +137,6 @@
   }
 
   @Test
-  public void indexerThrowsNoSuchChangeExceptionTryingToPostChange() throws Exception {
-    doThrow(new NoSuchChangeException(id)).when(schemaFactoryMock).open();
-    handler.index(TEST_CHANGE_ID, Operation.INDEX, Optional.empty());
-    verify(indexerMock, times(1)).delete(id);
-  }
-
-  @Test
-  public void indexerThrowsNestedNoSuchChangeExceptionTryingToPostChange() throws Exception {
-    OrmException e = new OrmException("test", new NoSuchChangeException(id));
-    doThrow(e).when(schemaFactoryMock).open();
-    handler.index(TEST_CHANGE_ID, Operation.INDEX, Optional.empty());
-    verify(indexerMock, times(1)).delete(id);
-  }
-
-  @Test
   public void indexerThrowsIOExceptionTryingToIndexChange() throws Exception {
     setupChangeAccessRelatedMocks(
         CHANGE_EXISTS, DO_NOT_THROW_ORM_EXCEPTION, THROW_IO_EXCEPTION, CHANGE_UP_TO_DATE);
@@ -222,17 +206,18 @@
       boolean changeExists, boolean ormException, boolean ioException, boolean changeIsUpToDate)
       throws OrmException, IOException {
     if (ormException) {
-      doThrow(new OrmException("")).when(schemaFactoryMock).open();
+      doThrow(new OrmException("")).when(changeDbMock).open();
     } else {
-      when(schemaFactoryMock.open()).thenReturn(dbMock);
-      if (changeExists) {
-        when(changeCheckerFactoryMock.create(TEST_CHANGE_ID)).thenReturn(changeCheckerPresentMock);
-        when(changeCheckerPresentMock.getChangeNotes()).thenReturn(Optional.of(changeNotes));
-        if (ioException) {
-          doThrow(new IOException("io-error"))
-              .when(indexerMock)
-              .index(any(ReviewDb.class), any(Change.class));
-        }
+      when(changeDbMock.open()).thenReturn(dbMock);
+    }
+
+    if (changeExists) {
+      when(changeCheckerFactoryMock.create(TEST_CHANGE_ID)).thenReturn(changeCheckerPresentMock);
+      when(changeCheckerPresentMock.getChangeNotes()).thenReturn(Optional.of(changeNotes));
+      if (ioException) {
+        doThrow(new IOException("io-error"))
+            .when(indexerMock)
+            .index(any(ReviewDb.class), any(Change.class));
       }
     }