Independent disk pools
An independent disk pool is a disk pool that contains objects, the directories or libraries that contain the objects, and other object attributes such as authorization and ownership attributes.
It is independent because the data in the independent disk pool is self-contained. This means that all of the necessary system information associated with the data resides within the independent disk pool. The unique qualities of an independent disk pool allow it to be switched in a multisystem environment and to be made available and unavailable in a single-system environment.
Independent disk pools are available only when you choose to make them available. They are not made available when you restart your system, unless you include code (Example: Make independent disk pool available at startup) to make them available. When you select to make a disk pool available, the disk pool goes through a process similar to that of restarting the system. While this processing takes place, the disk pool is in an Active state.
While the disk pool is in Active state, recovery steps are being performed. The disk pool is synchronized with other disk pools that may be in the disk pool group. Also, journaled objects are synchronized with their associated journal. System libraries are created for the primary disk pool: QSYSnnnnn, QSYS2nnnnn, QRCLnnnnn, QRCYnnnnn, QRPLnnnnn, SYSIBnnnnn (where nnnnn is the primary disk pool number, right-aligned and padded with zeros). For example, the QSYS library for independent disk pool 33 is QSYS00033.
At this time database cross-reference files will also be updated. The system libraries for the independent disk pool, QSYSnnnnn and QSYS2nnnnn, contain metadata not only for the independent disk pool, but also for the system disk pool. When the disk pool is made available, database cross-referencing clears the information related to SYSBAS and updates it with current information. The number and complexity of database file objects and SQL packages, procedures, and functions that need to be updated will play a role in the time it takes to make the disk pool available.
As the independent disk pool is made available, several system jobs are started to support the independent disk pool. In order for system jobs to remain unique on the system, those that service the independent disk pool are given their own simple job name when the disk pool is made available. The system jobs are essential to the operation of the disk pool. Do not tamper with these system jobs. The following is a list of system jobs that are created (nn = number):
- QDBXnnnXR
- handles database cross-reference file system functions
- QDBXnnnXR2
- handles database cross-reference field (column) information
- QDBnnnSV01
- handles database, journal, and commitment control events
- QDBnnnSV02 through QDBnnnSVnn
- high priority jobs that service the database
- QDBnnnSVnn through QDBnnnSVnn
- low priority jobs that service the database
When the recovery process is completed, the disk pool is in an Available state, ready for you to use. When you make a disk pool group available, you will see a completion messages for each disk pool. If the make available process encounters problems, such as an object not synchronized with a journal, you will need to resolve the issues reported in the error messages. See the job log, the system operator message queue, and the history log to locate problems and to verify the make available process.