| black |
Posted: Sep 05, 2007 04:47:48 AM |
Total Post: 14
Joined: Aug, 2007
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| can anybody explain breifly about checkpoint? |
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 Ramesh Joyisa |
| Posted: Sep 05, 2007 05:07:48 AM |  |
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Total Post: 226
Joined: Aug, 2007
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A checkpoint performs the following three operations:
(i) Every dirty block in the buffer cache is written to the data files.That is, it synchronizes the datablocks in the buffer cache with the datafiles on disk. It's the DBWR that writes all modified databaseblocks back to the datafiles.
(ii) The latest SCN is written (updated) into the datafile header.
(iii) The latest SCN is also written to the controlfiles.
The update of the datafile headers and the control files is done by the LGWR(CKPT if CKPT is enabled). As of version 8.0, CKPT is enabled by default.
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| Navi |
| Posted: Sep 05, 2007 02:26:03 PM | |
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Total Post: 60
Joined: Jun, 2007
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Hi,
Checkpoint is an event that represents the moment in time when the database is in a consistent state.i.e. All the dirty buffers are written to datafiles. So if a instance fails at this moment means no recovery is needed.
When checkpoint takes place:-
1) When instance is shutdown using any of the options except ABORT.
2) When Log Switch happens.
3) When DBA issues "ALTER SYSTEM CHECKPOINT".
4) When tablespace is taken offline.
5) When the value specified by the init.ora parameter FAST_START_MTTR_TARGET is exceeded.
When checkpoint takes place following actions occur:-
1) The checkpoint background process ckpt signals the DBWn to flush the dirty buffers into the datafiles.
2) Ckpt updates the control files and datafiles to reflect that it has successfully completed the checkpoint.
Regards,
Naveen
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| nick |
| Posted: Sep 11, 2007 11:36:07 AM | |
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Total Post: 30
Joined: Sep, 2007
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all the points has been included, included couple of more that:
1. checkpoint occurs whenever there is more that 1 MB of data has been commited.
2. Whenever there is a log switch.
3. whenever there is any DDL command fired.
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