"row cache lock" wait event...

One of those things that needs to be worried in RAC environment...

Noticed this event "row cache lock" the other day in our database on a simple insert. SQL is mostly showing waits on this even with so much of wait time.

Digging more, found that there was a sequence which "cache" size was not optimized for RAC environment. It has 20 as cache size. Increased to 20000 and this event disappears...

Finding the issue:

Run the following sql to find the CacheID:

select p1text,p1,p2text,p2,p3text,p3
  from gv$session
 where event = 'row cache lock';

Use the above returned CacheID in the below sql to find the Enqueue type:
select parameter ,count ,gets ,getmisses ,modifications
  from gv$rowcache
 where cache#=13;

This shows me it is dc_sequences.

Now, find the SEQuence which is being used in the SQL and check the cache size and change it.
alter sequence your_sequence
 increment by 1
 minvalue 1
 maxvalue 999999999999999999999999999
 cache 20000
 nocycle
 noorder;