Maintaining Data Integrity

Data that is defined as “sharable” can be accessed by any DB2 in the group. Several subsystems can read and write simultaneously against the same data. This is controlled via “inter-DB2 Read/Write interest.” Changed data, or data with “inter-DB2 R/W interest” is always cached in the group buffer pool; this data becomes “group bufferpool dependent.” The coupling facility will control the invalidations of changed pages in all members' local buffer pools.

Consistency of data among the DB2 members in the data sharing group is protected in two ways:

  • Concurrency controls

  • Coherency controls

In order to provide concurrency controls among the DB2 members in the data sharing group, a new locking structure is used. Since tuning ...

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