Remove Oracle Online Redo Test
delete online log
View the impact on database operations after deleting the log:
It can be seen that deleting the online log does not affect the normal operation of the database.
Impact on database startup and shutdown:
It can be seen that the database can be shut down normally after deleting the online log, but it cannot be started normally.
recovery below
After the database is opened through RestLogs, the recovery is complete, and the online log file has been created by itself.
Any data changes will be recorded in the database before redo can be written to the data file. But the redo logs are lost, how can the database still operate normally? Shouldn't it just shut down?
It is speculated that it is because of the mechanism of Linux to delete files. When a file is deleted, Linux does not really delete it. It will only be deleted after the process that uses it is closed.
Verify below:
delete online log
2. lsof check
lsof is used to view the opened files on the operating system. From the above, the online log file is still open, indicating that it has not been deleted.
The process ID is 76779. Let's see the real location of the log file on the operating system:
It can be seen that the files 258/259/260 corresponding to the online log are still there, and these three resources will not be released before the database is closed. This explains why deleting online log files does not affect the normal operation of the database.
lrwx------ 1 oracle oinstall 64 Feb 26 05:29 258 -> /u01/app/oracle/oradata/orcl11g/redo01.log (deleted)
lrwx------ 1 oracle oinstall 64 Feb 26 05:29 259 -> /u01/app/oracle/oradata/orcl11g/redo02.log (deleted)
lrwx------ 1 oracle oinstall 64 Feb 26 05:29 260 -> /u01/app/oracle/oradata/orcl11g/redo03.log (deleted)
Now close the database and see if the file has been deleted
With the shutdown of the database instance, the Oracle process 76779 disappears, and all the resources occupied by Oracle are released. As a result, the Online Redolog is completely deleted, and the database cannot be started.