| Instance Recovery and Log Switch for uncommited transaction [message #62060] |
Wed, 23 June 2004 02:12 |
CC S
Messages: 1
Registered: June 2004
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Junior Member |
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Hi,
I have doubt about those uncommit transactions recorded in redo log and when log switch has been performed and checkpoint occured. Are those uncommit records will be used in instance recovery?
During instance recovery it applies CURRENT redo logs and based on that it will do the rollforward and rollback.
I mean after log switch and checkpoint occured,suddently power cut off, the server restart. Will the Oracle reconstruct the memory by using the uncommit redo record in the PREVIOUS log file?
For example:
SVRMGR> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 INACTIVE
2 CURRENT
3 INACTIVE
4 INACTIVE
4 rows selected.
SVRMGRL>UPDATE TABLE EMP SET SAL=1000 WHERE ENAME=JOHN;
PS:previous sal is 10 and not commit yet.
SVRMGR> alter system switch logfile;
Statement processed.
SVRMGR> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 INACTIVE
2 INACTIVE
3 CURRENT
4 INACTIVE
4 rows selected.
It is clear that the "UPDATE TABLE EMP SET SAL=1000 WHERE ENAME=JOHN" record in redo log group 2(PS:Not commit yet).Suddently power cut off, the server restart.Oracle how to rollback this uncommit transaction druing the instance recovery?PS:now the CURRENT redo log is group 3,it is no contains the "UPDATE TABLE EMP SET SAL=1000 WHERE ENAME=JOHN" uncommit information.
Please correct if i am wrong.
Thks & Best Regards,
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