Enq: WF Contention tops in AWR report

This is one of the peculiar issue face in recent times, Enq: WF Contention topping the AWR report and the application users were unable to connect and work the database as the performance of the database was drastically going down. 

Enq: WF Contention    

Enq; WF Contention it's basically the MMON processes is periodically flush ASH data into AWR tables. Oracle introduced the WF enqueue which is used to serialize the flushing of snapshot. But if this is the top event (30% of the database time), then it is a really issue. The ADDM report suggests to investigate the wait in service "SYS$BACKGORUND".       

To overcome the Enq; WF Contention we need to Flush and re-create the AWR repository. 

Execute the below steps to re-create the AWR repository

Login as sysdba 

@?/rdbms/admin/catnoawr.sql;

@?/rdbms/admin/catawrtb.sql;

At the end run utlrp .sql to compile invalid objects.

Note: Instance reboot is mandatory after completing the above activity.

Go through this doc for more details ORA-13518 : 'Invalid Database Id' On Call to DBMS_WORKLOAD_REPOSITORY Package [ID 984447.1]