Chapter 10. Concurrency

• CONCURRENCY

• ISOLATION LEVELS

• LOCKS

• LOCK CONVERSION

• LOCK ESCALATION

• LOCK WAIT

A database server acts as a central source of data access for users. The number of users can vary from one to thousands. When more than one user accesses the same data source at the same time, some rules must be established for the reading, inserting, deleting, and updating of the data to guarantee data integrity.

The rules for data access are set by each application connected to a DB2 database and are established using two methods:

Explicit control—Locking resources using an SQL statement or using a DB2 command

Implicit control—Locking resources by specifying an isolation level

Some of the DB2 database resources, databases, table ...

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