enq: FB - contention

SQL>  select wait_class,name from v$event_name  where name = 'enq: FB - contention';

WAIT_CLASS                                                       NAME
---------------------------- ----------------------------------------------------------------
Other                                                            enq: FB - contention

 

SQL> select name,PARAMETER1,PARAMETER2,PARAMETER3 from v$event_name where name = 'enq: FB - contention';

NAME                             PARAMETER1                       PARAMETER2                       PARAMETER3
-------------------------------- -------------------------------- -------------------------------- --------------------------------
enq: FB - contention             name|mode                        tablespace #                     dba

 

 

 

"This is the Format Block enqueue, used only when data blocks are using ASSM (Automatic Segment Space Management or bitmapped freelists).  As we might expect, common FB enqueue relate to buffer busy conditions, especially since ASSM tends to cause performance problems under heavily DML loads."

 

"well the format block enqueue ("enq: fb contention") is related to grabbing
new blocks in ASSM tablespaces, during an insert operation for example. It
might be a good idea at this point to find out what the 'query' is that you
are actually doing and if it is happening in parallel etc. Incidentally are
both of these queries on the one system, or is one PROD and one UAT?"

http://www.freelists.org/post/oracle-l/Execution-time-in-SHARED-SERVER-vs-DEDICATED-SERVER-RAC-10gR2,12