| Optimal setting on rollback segments [message #52945] |
Wed, 21 August 2002 06:37  |
Sean
Messages: 22
Registered: July 2000
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Junior Member |
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Does anyone know if there is any effect on performance if the optimal value is NOT set for rollback segments? In other words, they never shrink, and the old extents sit around until the database is re-started.
Thanks
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| Re: Optimal setting on rollback segments [message #52951 is a reply to message #52945] |
Wed, 21 August 2002 11:32  |
Trifon Anguelov
Messages: 514
Registered: June 2002
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Senior Member |
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Not exactly on the performance, but more on the rollback space managment side. Once a transaction force rollback segment to allocate additional extents, the rollback segment will keep the allocated space and never release it back.
At certain point a single very large transaction may use all of the available free space in the RBS tablespace, preventing the other rollback segments from extending. You can also run out of extents also if you don't have UNLIMITED extents in RBS. but also can lead to "Snapshot too old" error as well. So be carefull when you use it.
Hope that helps,
clio_usa
OCP - DBA
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