Summary
In this chapter, we have discussed how concurrency and serialization is controlled. To protect the data as it is being modified, rules are established and the changes and grouped into units of work. The data updated 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 will implement 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, table space, or partition.
If a requested lock is more restrictive, and another application ...
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