max_locks_per_transaction

Type: integer
Default: 64
Min: 10
Max: 2147483647
Context: postmaster
Restart: true

The shared lock table has space for max_locks_per_transaction objects (e.g., tables) per server process or prepared transaction; hence, no more than this many distinct objects can be locked at any one time. This parameter limits the average number of object locks used by each transaction; individual transactions can lock more objects as long as the locks of all transactions fit in the lock table. This is not the number of rows that can be locked; that value is unlimited. The default, 64, has historically proven sufficient, but you might need to raise this value if you have queries that touch many different tables in a single transaction, e.g., query of a parent table with many children. This parameter can only be set at server start.

When running a standby server, you must set this parameter to have the same or higher value as on the primary server. Otherwise, queries will not be allowed in the standby server.

Recommendations

Some databases with very complex schema or with many long-running tranactions need a higher amount. This is rare though.

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