Instance recovery ( crash recovery)
- When did it happen? Oracle instance recovery?
- Shutdown abort;
- Database Exceptions Down drop (machine crashes, power-down ...)
- The reason for instance recovery is that the data has been discarded and used Redo Data Recovery
- Instance recovery is an automated process that does not require manual intervention.
- < Span style= "font-family: ' Microsoft Yahei '; font-size:16.0pt; Font-weight:normal; Font-style:normal; " > control file is to check consistency, and if inconsistent, the instance recovers
- How does instance recovery occur at that stage?
- Sql>startup Nomount(Readspfle),launch the instance,Oraclegive yourself a bit of memory,Oraclethe memory up, this timeno instance recovery.
Sql> startup Nomount; ORACLE instance started.
- sql> ALTER DATABASE Mount ( Read the control file, put the database on Mount ), no instance recovery.
- sql>alter Database Open(Check the control file, the data file header, check the integrity of the database), and if inconsistent, an instance recovery occurs. OracleWhen you open the database (ALTER DATABASE Open), the information on each file header is checked (SCN)and the corresponding information in the control file (SCN)Compare, if not consistent, perform instance recovery.
- The process of instance recovery
- – Roll Forward rolling forward
- Read status is Currentand theActiveLog of status (redo Log), will occurCrashwhen there is no time to write to the data block on the disk, usingRedoinformation to recover.
- – Open the database ( ALTER DATABASE Open)
- – rolling back Rolling back
- Rollback of a transaction that is not committed.
- Instance Recovery
- Sql>shutdown abort;
- View Alert file
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Medium Recovery ( Media recovery) The instance recovery is not valid when the following conditions occur and media recovery is required:
- – The data file is missing and corrupted.
- – Online log Files (online Redo) lost, damaged.
- – data file is too old ( For example, files recovered from a backup set.) )
- – file newness (for example, all other files are recovered from the backup)
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Recovery for Oracle instances, media Recovery (Crash recovery) (Media recovery)
