diff --git a/endpoint/opcua/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/endpoint/opcua/AasServiceNodeManager.java b/endpoint/opcua/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/endpoint/opcua/AasServiceNodeManager.java
index 826c8d592..b2030a3e3 100644
--- a/endpoint/opcua/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/endpoint/opcua/AasServiceNodeManager.java
+++ b/endpoint/opcua/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/endpoint/opcua/AasServiceNodeManager.java
@@ -43,6 +43,7 @@
 import de.fraunhofer.iosb.ilt.faaast.service.messagebus.MessageBus;
 import de.fraunhofer.iosb.ilt.faaast.service.model.SubmodelElementIdentifier;
 import de.fraunhofer.iosb.ilt.faaast.service.model.exception.AmbiguousElementException;
+import de.fraunhofer.iosb.ilt.faaast.service.model.exception.PersistenceException;
 import de.fraunhofer.iosb.ilt.faaast.service.model.exception.ValueFormatException;
 import de.fraunhofer.iosb.ilt.faaast.service.model.messagebus.SubscriptionId;
 import de.fraunhofer.iosb.ilt.faaast.service.model.messagebus.SubscriptionInfo;
@@ -388,9 +389,10 @@ private void subscribeMessageBus() throws MessageBusException {
      * @throws AddressSpaceException If the operation fails
      * @throws ValueFormatException The data format of the value is invalid
      * @throws AmbiguousElementException if there are multiple matching elements in the environment
+     * @throws PersistenceException if accessing the environment fails
      */
     private void elementCreated(Reference element, Referable value)
-            throws StatusException, ServiceResultException, ServiceException, AddressSpaceException, ValueFormatException, AmbiguousElementException {
+            throws StatusException, ServiceResultException, ServiceException, AddressSpaceException, ValueFormatException, AmbiguousElementException, PersistenceException {
         Ensure.requireNonNull(element, ELEMENT_NULL);
         Ensure.requireNonNull(value, VALUE_NULL);
 
@@ -472,9 +474,10 @@ private void elementDeleted(Reference element) throws StatusException {
      * @throws AddressSpaceException If the operation fails
      * @throws ValueFormatException The data format of the value is invalid
      * @throws AmbiguousElementException if there are multiple matching elements in the environment
+     * @throws PersistenceException if accessing the environment fails
      */
     private void elementUpdated(Reference element, Referable value)
-            throws StatusException, ServiceResultException, ServiceException, AddressSpaceException, ValueFormatException, AmbiguousElementException {
+            throws StatusException, ServiceResultException, ServiceException, AddressSpaceException, ValueFormatException, AmbiguousElementException, PersistenceException {
         Ensure.requireNonNull(element, ELEMENT_NULL);
         Ensure.requireNonNull(value, VALUE_NULL);
 
diff --git a/endpoint/opcua/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/endpoint/opcua/OpcUaEndpoint.java b/endpoint/opcua/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/endpoint/opcua/OpcUaEndpoint.java
index ea633db50..359cc711f 100644
--- a/endpoint/opcua/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/endpoint/opcua/OpcUaEndpoint.java
+++ b/endpoint/opcua/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/endpoint/opcua/OpcUaEndpoint.java
@@ -29,6 +29,7 @@
 import de.fraunhofer.iosb.ilt.faaast.service.model.api.request.submodel.InvokeOperationSyncRequest;
 import de.fraunhofer.iosb.ilt.faaast.service.model.api.response.submodel.GetSubmodelElementByPathResponse;
 import de.fraunhofer.iosb.ilt.faaast.service.model.api.response.submodel.InvokeOperationSyncResponse;
+import de.fraunhofer.iosb.ilt.faaast.service.model.exception.PersistenceException;
 import de.fraunhofer.iosb.ilt.faaast.service.model.value.ElementValueParser;
 import de.fraunhofer.iosb.ilt.faaast.service.model.value.MultiLanguagePropertyValue;
 import de.fraunhofer.iosb.ilt.faaast.service.model.value.mapper.ElementValueMapper;
@@ -101,10 +102,9 @@ public void start() throws EndpointException {
             return;
         }
 
-        aasEnvironment = service.getAASEnvironment();
-        Ensure.requireNonNull(aasEnvironment, "aasEnvironment must not be null");
-
         try {
+            aasEnvironment = service.getAASEnvironment();
+            Ensure.requireNonNull(aasEnvironment, "aasEnvironment must not be null");
             server = new Server(currentConfig.getTcpPort(), aasEnvironment, this);
             server.startup();
             LOGGER.debug("server started");
@@ -270,8 +270,9 @@ else if (response.getStatusCode() == StatusCode.CLIENT_METHOD_NOT_ALLOWED) {
      * Read the current environment from the service.
      *
      * @return The current environment.
+     * @throws PersistenceException if accessing the environment fails
      */
-    public Environment getAASEnvironment() {
+    public Environment getAASEnvironment() throws PersistenceException {
         return service.getAASEnvironment();
     }
 }
diff --git a/persistence/mongo/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/persistence/mongo/PersistenceMongo.java b/persistence/mongo/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/persistence/mongo/PersistenceMongo.java
index 5a6c3ed3a..8474fa882 100644
--- a/persistence/mongo/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/persistence/mongo/PersistenceMongo.java
+++ b/persistence/mongo/src/main/java/de/fraunhofer/iosb/ilt/faaast/service/persistence/mongo/PersistenceMongo.java
@@ -91,6 +91,7 @@
 import org.eclipse.digitaltwin.aas4j.v3.model.SubmodelElement;
 import org.eclipse.digitaltwin.aas4j.v3.model.SubmodelElementCollection;
 import org.eclipse.digitaltwin.aas4j.v3.model.SubmodelElementList;
+import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 
@@ -98,14 +99,12 @@
  * Persistence implementation for a mongo database.
  */
 public class PersistenceMongo implements Persistence<PersistenceMongoConfig> {
-    private static final String ID_KEY = "id";
-    private static final String ID_SHORT_KEY = "idShort";
-    private static final String SUBMODEL_ELEMENTS_KEY = "submodelElements";
-    private static final String VALUE_KEY = "value";
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(PersistenceMongo.class);
+
+    private static final int RANDOM_VALUE_LENGTH = 100;
     private static final String SERIALIZATION_ERROR = "Serialization of document with id %s failed!";
-    private static final String DESERIALIZATION_ERROR = "Deserialization of document with id %s failed!";
 
-    private static final org.slf4j.Logger LOGGER = LoggerFactory.getLogger(PersistenceMongo.class);
     private static final String MSG_RESOURCE_NOT_FOUND_BY_ID = "resource not found (id %s)";
     private static final String MSG_MODIFIER_NOT_NULL = "modifier must be non-null";
     private static final String MSG_CRITERIA_NOT_NULL = "criteria must be non-null";
@@ -117,6 +116,11 @@ public class PersistenceMongo implements Persistence<PersistenceMongoConfig> {
     private static final String SUBMODEL_COLLECTION_NAME = "submodels";
     private static final String OPERATION_COLLECTION_NAME = "operationResults";
 
+    private static final String ID_KEY = "id";
+    private static final String ID_SHORT_KEY = "idShort";
+    private static final String SUBMODEL_ELEMENTS_KEY = "submodelElements";
+    private static final String VALUE_KEY = "value";
+
     private static final Pattern INDEX_REGEX = Pattern.compile("\\[\\d+\\]");
 
     private final JsonApiSerializer serializer = new JsonApiSerializer();
@@ -612,7 +616,6 @@ public void deleteConceptDescription(String id) throws ResourceNotFoundException
         deleteElementById(cdCollection, id);
     }
 
-    private static final int RANDOM_VALUE_LENGTH = 100;
 
     private static String generateRandomValue() {
         byte[] data = new byte[RANDOM_VALUE_LENGTH];