Manual:$wgAntiLockFlags

Details
Anti-lock flags. This is a bitfield. The constants are set in defines>Special:MyLanguage/Manual:Defines.php|Defines.php.
 * ALF_PRELOAD_LINKS : Preload links during link update for save. (This option has no effect since 1.6.0)
 * ALF_PRELOAD_EXISTENCE : Preload cur_id during replaceLinkHolders. (This option has no effect since 1.5.0)
 * ALF_NO_LINK_LOCK : Don't use locking reads when updating the link table. This is necessary for wikis with a high edit rate for performance reasons, but may cause link table inconsistency. (This option was introduced in 1.5.0)
 * ALF_NO_BLOCK_LOCK : As for ALF_LINK_LOCK, this flag is a necessity for high-traffic wikis. (This option was introduced in 1.5.0 and has no effect since 1.18.0)

Example
To reduce lock contention, at the expense of introducing occasional inconsistencies, set