How about current transactions
gary smith, March 04, 2008 - 11:32 am UTC
The crux of my question regards a transaction that has already started rolling back.
Can changing fast_start_parallel_rollback to 'HIGH' (it's dynamic) hasten a rollback that's already in progress?
March 04, 2008 - 12:38 pm UTC
if you crash the system and restart it - it is for "fast start", so if you shutdown abort/startup or startup force, it would.
it is for SMON, if your session is doing the rollback - not SMON - it won't affect it.
Marcus, October 17, 2013 - 1:38 pm UTC
Maybe this could help. Do at you own risk.
alter system set fast_start_parallel_rollback=HIGH sid='*' ;
kill -9 <pid>
It will make smon do the rollback using all the resources available.
Parallel Rollback ? Could be...
J. Laurindo Chiappa, September 29, 2016 - 6:50 pm UTC
Yes, in some scenarios this could be useful, BUT in others not - for example, see metalink/MOS note "Database Hangs Because SMON Is Taking 100% CPU Doing Transaction Recovery" (Doc ID 414242.1) referencing one case where the parallel recover slaves could interfere/create concurrency one with another and the solution is to DISABLE parallel rollback/recover...
And just adding :
=> the same note have links about refs regarding SMON being blocked and/or suffering from CPU starvation
=> the ROLLBACK operation basically implies in an awful lot of I/Os to READ the data and another mountain of operations (in the Oracle dictionary and in memory) to PROCESS the read data - for sure, things like undo data being in the fastest disk/device (to help the I/O), internal/dictionay objects´ statistics and/or rescheduling of the data load and things like that COULD be in order, too...
J. Laurindo Chiappa