Getting intermittent connection issue with DS on Prod.

Hi Team ,

We are getting intermittent connection issues while  using a expression rule, which retrieves data from DB source . Please find below logs for your reference . 

Caused by: com.appiancorp.suiteapi.common.exceptions.AppianRuntimeException: com.appiancorp.suiteapi.common.exceptions.AppianException: The data store entity does not exist, has been deleted, or you do not have sufficient privileges to access its data. (APNX-1-4261-001)
at com.appiancorp.expr.server.fn.query.QueryEntity.getDataStore(QueryEntity.java:253)
at com.appiancorp.expr.server.fn.query.QueryEntity.queryentity_appian_internal(QueryEntity.java:155)
at com.appiancorp.expr.server.fn.query.QueryEntity.executeQuery(QueryEntity.java:115)
at com.appiancorp.expr.server.fn.query.QueryEntity.executeQuery(QueryEntity.java:99)
at com.appiancorp.expr.server.fn.query.AbstractQueryExecutor.op(AbstractQueryExecutor.java:66)
at com.appiancorp.core.expr.fn.Signature.eval(Signature.java:182)
at com.appiancorp.core.expr.fn.Function.eval0(Function.java:62)
at com.appiancorp.core.expr.DefaultEvaluable.eval(DefaultEvaluable.java:214)
at com.appiancorp.core.expr.FunctionCallDelegate$InternalFunctionCallWithContext.eval(FunctionCallDelegate.java:284)
at com.appiancorp.core.expr.FunctionCallDelegate.evalCacheableFunctionCall(FunctionCallDelegate.java:140)
at com.appiancorp.core.expr.FunctionCallDelegate.evalFunctionCall(FunctionCallDelegate.java:105)
at com.appiancorp.core.expr.AppianScriptContextTop.evalInternalFunction(AppianScriptContextTop.java:530)
at com.appiancorp.core.expr.AppianScriptContextChild.evalInternalFunction(AppianScriptContextChild.java:293)
at com.appiancorp.core.expr.tree.FunctionCall.evalImmediate(FunctionCall.java:580)
at com.appiancorp.core.expr.tree.FunctionCall.evalEvaluable(FunctionCall.java:528)
... 56 more
Caused by: javax.persistence.PersistenceException: Cannot connect to the database.
at com.appiancorp.rdbms.hb.HbConfigurationHelper.handleDialectException(HbConfigurationHelper.java:127)
at com.appiancorp.rdbms.hb.HbConfigurationHelper.buildSessionFactory(HbConfigurationHelper.java:112)
at com.appiancorp.type.external.teneoimpl.AppianHbSessionDataStore.buildSessionFactory(AppianHbSessionDataStore.java:152)
at org.eclipse.emf.teneo.hibernate.HbSessionDataStore.initialize(HbSessionDataStore.java:120)
at com.appiancorp.type.external.teneoimpl.AppianHbSessionDataStore.initialize(AppianHbSessionDataStore.java:139)
at com.appiancorp.type.external.teneoimpl.TeneoDataStoreFactory.makeStoreComponents(TeneoDataStoreFactory.java:315)
at com.appiancorp.type.external.teneoimpl.TeneoDataStoreFactory.getPossiblyCachedDataStore(TeneoDataStoreFactory.java:283)
at com.appiancorp.type.external.teneoimpl.TeneoDataStoreFactory.getTeneoDataStore(TeneoDataStoreFactory.java:116)
at com.appiancorp.type.external.teneoimpl.TeneoDataStoreFactory.getDataStore(TeneoDataStoreFactory.java:143)
at com.appiancorp.expr.server.fn.query.QueryEntity.getDataStore(QueryEntity.java:241)
... 70 more
Caused by: org.hibernate.HibernateException: Access to DialectResolutionInfo cannot be null when 'hibernate.dialect' not set