Lock Table

A lock is created when a user thread writes an entry in the lock table. The lock table is the pool of available locks. Each entry is one lock. A single transaction can own multiple locks. For an explanation of locking and the SQL statements associated with locking, refer to the IBM Informix: Guide to SQL Tutorial. For information on performance considerations for locking, refer to your IBM Informix: Performance Guide.

The following information, which is stored in the lock table, describes the lock:

• The address of the transaction that owns the lock
• The type of lock (exclusive, update, shared, or intent)
• The page and rowid that is locked
• The tblspace where the lock is placed

To specify the number of entries in the lock table, set the LOCKS configuration parameter. However, the lock table grows dynamically if more locks are needed. For information on specifying the number of locks available to sessions, refer to the chapter on configuration parameters in the IBM Informix: Administrator's Reference. For information on how to estimate the number of locks, refer to the chapter on configuration effects on memory utilization in your IBM Informix: Performance Guide.

For information on how the lock table grows dynamically and monitoring locks, refer to the chapter on locking in your IBM Informix: Performance Guide.