| DBA General questions:: New at this [message #52461] |
Tue, 23 July 2002 09:16  |
Maulin Sekran
Messages: 1
Registered: July 2002
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Junior Member |
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Hi,
I am currently taking a database class and i am having great difficulty tyring to figure out these two questions. Any help would be greatly appreciated.
1.)Name three situations when the DBWR writes to the data files and when the LGWR writes to the redo log files.
2.) Describe the scenario in detail that leads to the error message "SNAPSHOT TOO OLD". If you get this error too many times, how would you fix it.
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| Re: DBA General questions:: New at this [message #52463 is a reply to message #52461] |
Tue, 23 July 2002 12:23  |
ctg
Messages: 146
Registered: July 2002
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Senior Member |
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sounds like test questions.
1)
DBWR (or DBW0) writes:
checkpoint event
timeout (3 seconds)
too many dirty buffers in the buffer cache
too few free bufers in the buffer cache
LGWR writes:
before DBWR
COMMIT
log buffer 1/3 full
log buffer contains 1 Meg of info
2)
Scenrio:
Joe Issues complicated select stmt getting emp info
Fred updates 1 employee (king) - before image put in RBS
Fred commits - Before image no longer required
Joe finally gets to king, which has been modified, and the before image has been overwritten. Joe gets the Snapshot to old error message.
You can try and avoid this error by:
-- creating more rollback segments
-- making larger rollback segments
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