System Administrator’s Guide U42252-J-Z915-1-76
Recovery Selecting the Type of Recovery
5.1.3 Automatic Recovery (Crash Recovery)
In the case of a fully-automatic recovery, NSR-ORA deals with the entire task of
restoring the damaged tablespaces and redolog files without any further
operator intervention. It communicates with ORACLE, enquires which
tablespaces are damaged and recreates them. Then it asks for the necessary
redolog files and recreates these, if they have already been backed up. It then
tells ORACLE to perform a roll forward using the redolog files.
Within a recovey process three phases are to be distinguished:
●Analyzing the Database (Crash Analysis)
During the database is examined an analysis with regard to a loss of data-
base files is performed. Therefore, first of all, NSR-ORA tries to close the
database. If this action fails the database is shut down hard using the
shutdown abort command. Then several informations required for a following
restore and the recovery of the database are generated by analyzing data-
base views.
If this examination shows that no database files were lost the database will
be reset to normal operation mode again already within this phase.
●Restoring the database files
The restore of the database files will be done using the information genera-
ted in the analyzation phase. This phase is unnecessary, if the previous exa-
mination has not found any database files corrupted.
●Recovering the database
The recovery on the database level is performed offline, i.e. the database is
not usable. During this phase all database files are switched to offline mode
to assure, that all the database files are recovered. In addition the archiving
monitor is stopped to prevent it from obstructing the recovery process.
Thereby the tablespaces are recovered parallel whereby the parameters
NSR_MAX_RECOVER and NSR_MAX_DEVICES rule the parallelism and/or
the number of backup devices to be used.
Subsequently all offline redolog files (after restoring) will be redrawn. After a
final check for the recovery activities having been completed successfully
the database is reset to normal operation mode.