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| Re: What happen when Tablespace begin in backup mode. [message #62568 is a reply to message #62565] |
Thu, 29 July 2004 07:20   |
Frank Naude
Messages: 4579
Registered: April 1998
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Senior Member |
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Hi,
The following will happen when you do a BEGIN BACKUP on a tablespace:
1) Oracle will stop updating the tablespace's file headers; and
2) Oracle will write more data to the redo log files (write complete blocks instead of deltas); and
3) Oracle will continue to write COMMITed changes to the tablespace's data files; and
3) Oracle will wait for you to backup the datafiles and issue an END BACKUP command :-)
Best regards.
Frank
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| Re: Really Oracle write data to logfile. [message #62577 is a reply to message #62574] |
Fri, 30 July 2004 05:15 |
Frank Naude
Messages: 4579
Registered: April 1998
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Senior Member |
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Hi,
Yes, that is correct!
The redo log files will be archived as usual. If your archive destination gets full, your database will hang until the directory is cleared (backup/ move archived log files). Again, this is expected and documented behaviour. To prevent any problems, don't backup your database if you have too many users working!
Best regards.
Frank
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| Re: What happen when Tablespace begin in backup mode. [message #62614 is a reply to message #62568] |
Tue, 03 August 2004 01:40 |
Satheesh Babu.S
Messages: 35
Registered: July 2004
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Member |
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I want to elaborate point 2 and 3 of frank,
"2) Oracle will write more data to the redo log files (write complete blocks instead of deltas); and"
In order to avoid split block problem oracle write whole block into to redo log file. When a block is changed first time in the db cache, the whole block will get into redo log file. If any subsequent changes happening to this block later will sent only the deltas to redo log file. Incase if this block is flushed to datafile and brought it back by other processes, then first changes to this block will again move whole block to redo log and subsequent change.
So that's the reason begin backup has to be done when there is relatively less work in the db.
"Oracle will continue to write COMMITed changes to the tablespace's data files; and"
Not only committed data, even uncommited datas will get into datafile. This is true even for redo log file.
Thanks and Regards,
Satheesh Babu.S
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