So, that brings us back to Kevin's question about what warnings are seen in the Dataflows. Please refer to the following link - particularly the section on "Viewing the error count per component". This will show us what Pega sees as the cause of the issue.
Your log is also showing DBMS issues - ConnectionDeadSQLExceptions from a connection pool that Pega is referencing in the WebLogic container. Perhaps this database was restarted ... would need to see how the data source is set up. The issue you have is likely a symptom.
Your environment continues to encounter errors as a direct result of the database issue over the entire day. Restarting the JVM will address the issue - Pega relies on the database to load java classes, and downtime at the database level that is not handled via failover can and will cause the environment to behave unpredictably and cause significant instability.