Backup frequency and space utilization
When you determine what the System Level Backup will be used for, there are several other things to consider when you configure IMS Recovery Expert to create the System Level Backups.
System Level Backup type
IMS Recovery Expert allows for the following types of backups:
- Full
- The System Level Backup will contain the database data, the archive logs, and the IMS system data sets. A Full backup can be used for system restore, application or database recovery, and disaster restart or recovery.
- Data only
- The backup contains only the database data for the IMS environment. A data only backup is used to restore all of the database data and run forward recovery processes. A data only backup is done at the volume level. A data only backup is also used for application or database recovery, which is performed at the data set level.
- Partial
- The backup will contain only data for an application or group of databases. A partial backup is used for application or database recovery only. Restoring the data sets is done at the data set level.
Optimal backup frequency and retention
With the recovery objectives in mind, consider how frequently the System Level Backups need to be created. Using fast-replication, the CPU and I/O costs to create a backup are minimal. The impact to online IMS availability is also insignificant, so the traditional approach of first determining the time when a backup can be created might not be necessary. When you are using IMS Recovery Expert, determine the ideal recovery time for your business, and set the backup frequency (hourly, daily, weekly, and so on) accordingly.
Using fast-replication, IMS Recovery Expert creates a System Level Backup on disk. Having a System Level Backup on disk can greatly reduce recovery time. IMS Recovery Expert can maintain up to 99 generations of a System Level Backup on disk. IMS Recovery Expert can also automate the offloading of a System Level Backup to tape and use a tape-based System Level Backup for recovery if needed. Again, consider the most ideal recovery time for your business when you determine the number of generations to maintain on disk, tape, or both.
If disk space is a premium for creating and maintaining System Level Backups, then the System Level Backups can be configured to immediately offload them to tape. Then, the disk volumes can be used to create System Level Backups for other IMS systems.
- To maintain a set of SNAP or FlashCopy® backups for the previous week, you can configure a profile with a SNAP or FlashCopy backup type and seven generations of full backups. This job is scheduled to run daily.
- To maintain a set of BCV backups for the previous week, you can configure a profile with a BCV backup type and eight generations of full backups. Eight generations are required to maintain one week of backups, since one target volume is always mirroring the current set of volumes. This leaves seven backups available for system restoration. This job is scheduled to run daily.
- A separate profile can be created to run once a week. This profile would create backups that can be used to restore the system to a point farther back than one week ago. Depending on space considerations, you could set the number of generations as low or high as needed.
Fast-replication considerations
- To reduce background copy time and resources, consider incremental fast-replication options.
- To save space, consider using space efficient fast-replication methods like EMC VDEVs.