I am not a facebook fan neither an addict of it, but i still got to see “enq: FB contention”…thats bad :). Well this was for the first time i saw this wait event and it was on 11.2.0.2 version.Mostly, the enq: FB contention wait event was followed by log buffer space.
Well, the enq: FB contention is associated with block formatting and it ensures that only one process format the blocks in an ASSM tablespace.As i can think of, we had multiple sessions doing insert and could be that each session tried to format the block which caused the contention.The value on P1 is name|mode , P2 tells the tablespace number, and P3 gives the dba
[email protected] > select session_id,SQL_ID,EVENT,P1,P1text,P2,P3,WAIT_TIME,SESSION_STATE,TIME_WAITED from v$active_session_history where event like '%FB%'; SESSION_ID SQL_ID EVENT P1 P1TEXT P2 P3 WAIT_TIME SESSION TIME_WAITED ---------- ------------- ------------------------- ---------- ------------- ---------- ---------- ---------- ------- ----------- 775 bg65mx8g077g5 enq: FB - contention 1178730502 name|mode 9 285422249 0 WAITING 189987 ...... ...... [email protected] > select name from v$tablespace where ts#=9; NAME ---------------------------------------- ABC_TBS_01 [email protected] > SELECT dbms_utility.data_block_address_block(285422249) "BLOCK", 2 dbms_utility.data_block_address_file(285422249) "FILE" 3 from dual; BLOCK FILE ---------- ---------- 209577 68
2 thoughts on “Enq: FB contention – No its not Facebook Contention”
Thanks – FaceBook is what first popped into my mind as well. Good explanation.
FB=Face Book Contention LoL.
Explanation was good, thx