As databases increase in size and queries place demands on the continued availability of the operating system, the time and hardware resources required to back up and recover databases are also growing substantially. Backing up an entire database or the table spaces of large databases can strain your system resources because the storage requirements to maintain multiple copies of a database or of table spaces are considerable.
DB2 Version 7.2 provides a number of new functions that will help you perform online or offline backups, while allowing your data to be accessed as needed. See the DB2 Release Notes for more information on each of the following new functions.
Many storage vendors now provide storage solutions that enhance the availability of data. One such offering is the ability to split a mirrored copy of data and make that mirrored copy available for processing or available to another server. To exploit this storage capability, DB2 has delivered two new features in Version 7.2:
Suspended I/O supports continuous system availability, while providing for online split mirror handling of the database. By momentarily suspending I/O to disk, DB2 will ensure that the split mirror copy maintains its integrity
The db2inidb utility operates on the mirrored copy and can do the following:
Active logs help database administrators perform database recovery. DB2 now has the capability to mirror the active log files to protect databases from:
A new registry variable, DB2_NEWLOGPATH2, allows the database to write an identical copy of the log files to a different path on a physically separate disk.
DB2 now uses multiple agents to perform both crash recovery and database rollforward recovery. You can expect better performance during these operations, particularly on symmetric multi-processor (SMP) machines. Using multiple agents during database recovery takes advantage of the extra CPUs that are available on SMP machines.
See the DB2 Release Notes for more information on parallel recovery.
DB2 Version 7.2 allows you to perform a backup from a split image, following the use of the db2inidb utility.
The backup from split image feature allows you to perform an offline backup of the entire database.
For DB2 Version 7.2, this support is limited to databases that contain DMS table spaces only.
You can use named pipes for backing up and restoring databases on UNIX-based systems. To use this function, the writer and reader of the named pipe must be on the same machine. You must create the named pipe on a local file system before backing up the database.
DB2 support for incremental backup responds to the need to manage system resources while database backup and restore operations occur. Two types of incremental backup are supported:
A backup image of all database data that contains only pages that have been updated since the previous backup of the database or table space was taken. The image also contains the initial database metadata that is normally stored in full backup images, such as the database configuration, table space definitions and database history. Each successive backup contains the entire contents of the previous incremental image, plus any data that is new or changed since the previous incremental backup.
A delta image of all data that has changed since the last successful backup of a table space. The last backup could have been a full, incremental, or delta backup. Each successive delta backup also contains the database metadata that is contained in full backup images.
You can use either incremental or delta backup in either online or offline backup operations. Incremental backup can help you by:
DB2 tracks the database updates with the new database configuration parameter, trackmod. See the DB2 Release Notes for more information on incremental and delta backups.