No Embedded database in Performance Warehouse Settings

We are using Dynatrace 6.1.0.8105. We found that embedded (derby) Performance warehouse got off-line suddenly(I guess due to high transaction volume). It was working perfectly earlier. Thereafter, embedded database option in Dynatrace Setting vanished away. The snapshots: Is there any way to bring embedded database back to work? (I guess its crashed?) (We will be assigned separate database soon) Following are lines from dynatrace sever logs:

2015-08-18 17:05:12 WARNING [AbstractRepositoryAccessor] Writing of 2653 measurements elapsed: 0 hours, 3 mins, 27 sec, 473 ms. ms value(207473)

2015-08-18 17:05:12 WARNING [AbstractRepositoryAccessor] If this message occurs frequently (e.g. more than once an hour) the throughput of the attached database seems to be too low.

2015-08-18 17:05:12 WARNING [DefaultStatementExecutor] Exception occured during PWH data processing.

Exception: com.dynatrace.diagnostics.server.shared.exceptions.repository.RepositoryException:

Expected a SQLException Cause: org.apache.derby.iapi.error.ShutdownException: : com.dynatrace.diagnostics.util.modern.LogManager$ContextLogger$1 run:137 org.apache.derby.iapi.error.ShutdownException: at org.apache.derby.iapi.services.context.ContextManager.checkInterrupt(Unknown Source) at org.apache.derby.iapi.services.context.ContextManager.getContext(Unknown Source) at org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.getStatementContext(Unknown Source) ....

2015-08-18 17:06:49 INFO [Server] Trying to connect to Performance Warehouse using the following settings: jdbc:derby:repository/dynaTrace6

2015-08-18 17:06:49 INFO [Server] Successfully connected to Performance Warehouse version 6.1.0.0 using the following settings: jdbc:derby:repository/dynaTrace6

2015-08-18 17:06:49 INFO [Repository] Repository access state changed to 'CONNECTED'