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Background documentation Critical Section Locate the document in the library structure

A critical section is a memory area to which different tasks have competing access and where access is controlled by synchronization mechanisms.

Access by a Task to a Critical Section is Exclusive

To control exclusive access by tasks to critical regions, the database system uses special semaphores, which are called regions. When a task accesses a critical section, the associated region blocks this critical section for all other tasks.

Access by a Task to a Critical Section is Exclusive or Non-Exclusive

To control both exclusive and non-exclusive access to critical sections, the database system uses regions with extended functionality, called reader-writer locks.

If a task write-accesses a critical section, the associated reader-writer lock blocks this critical section for all other write-accesses but allows other read-accesses.

If a task read-accesses a critical section, the associated reader-writer lock blocks this critical section for all other write-accesses but allows other read-accesses.

Note

Blocking critical sections has nothing to do with the SQL locks on database objects.

See also:

Database Administration in CCMS: Structure linkCritical Sections

 

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