# Notes on locking

In addition to the locks already described, foreign key lookups require briefly held shared locks on the referenced table (row or table, depending on the configuration).

The table and examples in this section do not take performance-based lock escalation into account. Remember that the system can choose table-level locking for performance reasons.

Parent topic: Types and scope of locks in Derby systems
Related concepts
Exclusive locks
Shared locks
Update locks
Related reference
Lock compatibility
Scope of locks