Product Documentation

Database Administrator's Guide

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LOCK_HASH <Number of Hash Bins>

The number of hash bins available to the lock hash algorithm. A lock table exists holding all lock entries for each user. To search this table a hash algorithm is employed. The LOCK_HASH value specifies the number of 8-byte hash bins available for use by this algorithm. This value should only be increased with careful consideration. There is a marginally decreasing return for increasing values.

Default: 16

The following keywords are closely related to the lock hash bin strategy and are listed here for convenience.

LOCK_HASH_MAX <maximum number of lock hash bins>

Default: 131072

LOCK_HASH_LOADFAC <avg locks per bin>

Default: 8

LOCK_HASH_REHASHFAC <fraction of hash bins reorganized>

Default: 4 (denominator - one fourth at a time)

Note: Dynamic hashing is recommended for lock table entries held before commit. This results in more efficient searching of intermediate lock table contents. Dynamic hashing automatically adjusts to changing conditions of transaction and lock data.