#14 Why do offline backups take longer than online backups?
Posted: Fri Dec 16, 2011 9:48 am
All things being equal, an offline backup will take longer to run than an online backup of the same database.
This is because, by default, offline and quiesced backups perform index block to target (object, subobject, etc) verification, making sure that index entries resolve to the correct records in the file. When an online backup is performed these checks are not done (it is not possible for these checks to be done during an online backup because the database files are being updated during the backup process.
It is the responsibility of the user to perform a database certification on the recovered backup).
At the request of users a new INI file setting was introduced in JADE 6.2.20, 6.3.07 and 7.0 that makes it optional to perform this verification at the time of performing an offline or quiesced backup. This enables a more efficient backup process that fits comfortably in the processing window, after which the user can (using existing functionality) perform a certify of the database using a temporary relocated (and checksum verified) copy of the backup.
The new parameter defaults to false so that the default behaviour is that verification is performed as part of the backup operation.
This is because, by default, offline and quiesced backups perform index block to target (object, subobject, etc) verification, making sure that index entries resolve to the correct records in the file. When an online backup is performed these checks are not done (it is not possible for these checks to be done during an online backup because the database files are being updated during the backup process.
It is the responsibility of the user to perform a database certification on the recovered backup).
In releases prior to JADE 6 this verification was optional, however it was decided that this should be the default behaviour because few users were regularly certifying their databases, and some users were not certifying their databases at all. It's an important part of system maintenance to certify a production database regularly. Please consult the Database Administration guide for further information regarding database certification.Note: Enhancements in JADE 7 have significantly reduced the time required to perform index block to target verification.
At the request of users a new INI file setting was introduced in JADE 6.2.20, 6.3.07 and 7.0 that makes it optional to perform this verification at the time of performing an offline or quiesced backup. This enables a more efficient backup process that fits comfortably in the processing window, after which the user can (using existing functionality) perform a certify of the database using a temporary relocated (and checksum verified) copy of the backup.
The new parameter defaults to false so that the default behaviour is that verification is performed as part of the backup operation.
Setting BackupIndexCrosscheckDisabled=true will disable the index block to target verification.[PersistentDb]
BackupIndexCrosscheckDisabled=[true|false]