Please help to understand this DB error. how to resolve this error.

Thanks in advance

Exception:

com.pega.pegarules.boot.internal.extbridge.AppServerBridgeToPega.invokeMethodPropagatingThrowable(AppServerBridgeToPega.java:216) at com.pega.pegarules.boot.internal.extbridge.AppServerBridgeToPega.invokeMethodPropagatingException(AppServerBridgeToPega.java:238) at com.pega.pegarules.internal.etier.ejb.EngineBeanBoot.invokeEngine(EngineBeanBoot.java:168) at com.pega.pegarules.internal.etier.interfaces.EJSLocalStatelessEngineBMT_f2439d86.invokeEngine(Unknown Source) at com.pega.pegarules.session.internal.engineinterface.etier.mdb.PRAsync.processRequest(PRAsync.java:155) at com.pega.pegarules.session.internal.engineinterface.etier.asynchbeans.AsyncTask.run(AsyncTask.java:64) at com.pega.pegarules.session.internal.engineinterface.etier.asynchbeans.RunnableWrapper.run(RunnableWrapper.java:71) at com.ibm.ws.asynchbeans.J2EEContext$RunProxy.run(J2EEContext.java:270) at java.security.AccessController.doPrivileged(AccessController.java:359) at com.ibm.ws.asynchbeans.J2EEContext.run(J2EEContext.java:770) at com.ibm.ws.asynchbeans.WorkWithExecutionContextImpl.go(WorkWithExecutionContextImpl.java:222) at com.ibm.ws.asynchbeans.ABWorkItemImpl.run(ABWorkItemImpl.java:159) at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1662) Caused by: java.lang.IllegalStateException: Error in counting records in the pr_sys_app_hierarchy_flat table at com.pega.pegarules.session.internal.authorization.context.GlobalContextCache.doesTopAppHashNeedToBeInsertedIntoFlattenedHierarchy(GlobalContextCache.java:1885) at com.pega.pegarules.session.internal.authorization.context.GlobalContextCache.populateApplicationRuleHierarchy(GlobalContextCache.java:1603) ... 60 more Caused by: com.pega.pegarules.pub.database.ConnectionException: Database-General Problem encountered when getting connection for database pegarules 0 Connection not available, Timed out waiting for 180004 From: (B4DA8E3B077350897B8BE4B13AEAA55F1) Caused by SQL Problems. Problem #1, SQLState null, Error code 0: com.ibm.websphere.ce.cm.ConnectionWaitTimeoutException: Connection not available, Timed out waiting for 180004 at com.pega.pegarules.data.internal.access.ExceptionInformation.createExceptionDueToDBFailure(ExceptionInformation.java:251) at com.pega.pegarules.data.internal.access.ConnectionManagerImpl.getConnectionFromDataSourceIdentity(ConnectionManagerImpl.java:1054) at com.pega.pegarules.data.internal.access.ConnectionManagerImpl.getConnection(ConnectionManagerImpl.java:1189) at com.pega.pegarules.data.internal.access.ConnectionManagerImpl.getConnection(ConnectionManagerImpl.java:1129) at com.pega.pegarules.data.internal.access.ConnectionManagerImpl.getConnection(ConnectionManagerImpl.java:343) at com.pega.pegarules.data.internal.access.ThreadConnectionStoreImpl.getConnection(ThreadConnectionStoreImpl.java:443) at com.pega.pegarules.data.internal.access.RDBPageResultPackager.getConnection(RDBPageResultPackager.java:923) at com.pega.pegarules.data.internal.access.DatabaseImpl.list(DatabaseImpl.java:5887) at com.pega.pegarules.data.internal.access.DatabaseImpl.executeRDB(DatabaseImpl.java:6521) at com.pega.pegarules.data.internal.access.DatabaseImpl.executeRDB(DatabaseImpl.java:6477) at com.pega.pegarules.data.internal.access.DatabaseImpl.executeRDB(DatabaseImpl.java:6458) at com.pega.pegarules.session.internal.authorization.context.GlobalContextCache.doesTopAppHashNeedToBeInsertedIntoFlattenedHierarchy(GlobalContextCache.java:1878) ... 61 more Caused by: com.ibm.websphere.ce.cm.ConnectionWaitTimeoutException: Connection not available, Timed out waiting for 180004 at com.ibm.ws.rsadapter.AdapterUtil.toSQLException(AdapterUtil.java:1525) at com.ibm.ws.rsadapter.jdbc.WSJdbcDataSource.getConnection(WSJdbcDataSource.java:685) at com.ibm.ws.rsadapter.jdbc.WSJdbcDataSource.getConnection(WSJdbcDataSource.java:635) at com.pega.pegarules.data.internal.access.DataSourceManager.getConnection(DataSourceManager.java:221) at com.pega.pegarules.data.internal.access.DatabaseConnectionImpl.activate(DatabaseConnectionImpl.java:1436) at com.pega.pegarules.data.internal.access.ConnectionManagerImpl.getConnectionFromDataSourceIdentity(ConnectionManagerImpl.java:1008) ... 71 more Caused by: com.ibm.websphere.ce.j2c.ConnectionWaitTimeoutException: Connection not available, Timed out waiting for 180004 at com.ibm.ejs.j2c.FreePool.createOrWaitForConnection(FreePool.java:1705) at com.ibm.ejs.j2c.PoolManager.reserve(PoolManager.java:2693) at com.ibm.ejs.j2c.ConnectionManager.allocateMCWrapper(ConnectionManager.java:1064) at com.ibm.ejs.j2c.ConnectionManager.allocateConnection(ConnectionManager.java:701) at com.ibm.ws.rsadapter.jdbc.WSJdbcDataSource.getConnection(WSJdbcDataSource.java:668)