Lock Level MVCC and Readlock
When a table is opened, the settings for isolation level, lock level, and readlock affect the locking strategy used by Ingres.
The installation defaults for these settings are the DBMS configuration parameters:
• system_isolation
• system_lock_level
• system_readlock
The session can override readlock using:
SET LOCKMODE SESSION WHERE LEVEL=... READLOCK=
If READLOCK = NOLOCK, read nolock protocols are used even if the lock level is MVCC.
If READLOCK = EXCLUSIVE or SHARED and lock level is MVCC, then MVCC protocols are used.
Last modified date: 08/28/2024