Summary
In this chapter, we discussed how concurrency(serialization) is controlled. To protect the data as it is being modified, rules are established and the changes are grouped into units of work. The updated data is made permanent by the COMMIT statement or removed by the ROLLBACK statement. The rules of concurrency are determined by the isolation level, the lock size, and the rules of lock duration.
DB2 implements the isolation level semantics of data access by implicitly acquiring locks on behalf of applications. Applications can decide to lock a resource for exclusive or share modes. The resources that can be locked are the row, page, table, tablespace, and partition.
If a requested lock is more restrictive, and another application already ...
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