14.5 Database management

In the context of an application, backups must present consistent records across all of the data repositories that are used by the application. For example, a transaction must either be reflected in all of the affected data repositories or in none. This can be ensured by driving the backup from the application and relying on the intelligence of the application, or by quiescing the application and all associated data repositories during the backup.

General-purpose backup tools usually provide backup capability at the volume level or at the file level. For example, FlashCopy for Enterprise Storage Server, with a subsequent copy to tape, can back up a volume from z/VM, or a Tivoli Storage Manager agent can back up single files in a file system. Both the storage manager and the agent can reside on a Linux image. To the agent, a database looks just like any file. However, taking a full backup of a database is time-consuming and, if taken at close intervals, can also be wasteful of storage space.

Industry standard databases come with tools or APIs, or both, to facilitate data backup and recovery. These tools and APIs can be integrated with standard backup/recovery storage management products to support a rich set of backup/recovery storage services for relational database data. For example, DB2 has an API for incremental backups at the tablespace level. DB2 also includes a backup utility for non-disruptive DB2 backup that is integrated as a Tivoli Storage Manager client. Hence, you can run both full backups and incremental non-disruptive backups from Tivoli Storage Manager on a Linux image's databases.

A UNIX application that is to be consolidated on Linux on the mainframe might include databases on UNIX. For an application that has been set up properly, it can be assumed that a management solution for full and possibly incremental backups of the database is in place. When porting the application to Linux, it can be useful to port the entire application, including the database, in one stride. However, depending on your priorities and goals, different scenarios are conceivable. For example, you can migrate the application only and use a connector (for example, IBM DB2 Connect) to connect to an existing database on UNIX.