FairCom DB API for C

Session-Wide Lock Modes

The table below lists the lock modes that are to be used with the session-wide record locking function ctdbLock().

FairCom DB API Lock Modes	FairCom DB API .NET Lock Modes	Explanation
CTLOCK_FREE	FREE_LOCK	Turn off session-wide record locking. Free all automatically-acquired locks (with certain exceptions, see below).
CTLOCK_READ	READ_LOCK	Non-blocking read locks. If the lock cannot be acquired an error is returned.
CTLOCK_READ_BLOCK	READ_BLOCK_LOCK	Blocking read lock. The thread will block until the lock can be acquired.
CTLOCK_WRITE	WRITE_LOCK	Non-blocking write lock. If the lock cannot be acquired an error is returned.
CTLOCK_WRITE_BLOCK	WRITE_BLOCK_LOCK	Blocking write lock. The thread will block until the lock can be acquired.
CTLOCK_RESET	RESET_LOCK	Equivalent to calling Lock with CTLOCK_FREE followed by Lock() with CTLOCK_WRITE. This releases currently-held record locks (with certain exceptions, see below).
CTLOCK_SUSPEND	SUSPEND_LOCK	Temporarily suspend session-wide record locking. While locking is suspended, new record reads, writes, and deletes will not be automatically locked. Existing record locks remain in place, though.
CTLOCK_RESTORE _READ	RESTORE_READ_LOCK	To be used after a call to Lock with the CTLOCK_SUSPEND mode. This lock mode restores the lock mode as READ.
CTLOCK_RESTORE _READ_BLOCK	RESTORE_READ _BLOCK_LOCK	To be used after a call to Lock with the CTLOCK_SUSPEND mode. This lock mode restores the lock mode as READ_BLOCK.
CTLOCK_RESTORE _WRITE	RESTORE_WRITE_LOCK	To be used after a call to Lock with the CTLOCK_SUSPEND mode. This lock mode restores the lock mode as WRITE.
CTLOCK_RESTORE _WRITE_BLOCK	RESTORE_WRITE _BLOCK_LOCK	To be used after a call to Lock with the CTLOCK_SUSPEND mode. This lock mode restores the lock mode as WRITE_BLOCK.
CTLOCK_RESTORE _PREVIOUS		To be used after a call to Lock with the CTLOCK_SUSPEND mode. This lock mode restores the same lock mode that was valid before suspending the lock.

FairCom DB API .NET Lock Modes are defined in the LOCK_MODE enum.

Notes:

If you wish to turn session-wide locking off and release the record locks, use FREE.
If you wish to turn session-wide locking off and keep the record locks, use SUSPEND.
If you wish to turn session-wide locking back on (so new record reads, writes, and deletes get automatically locked), while keeping the record locks that existed before the SUSPEND, use one of the RESTORE modes.
If you wish to turn session-wide record locking back on and release the existing record locks, use RESET.

The modes listed in this table (except for the “RESET” and “_RESTORE_” modes) are also returned by the ctdbGetLockMode() function to show the current state of the session-wide locking system.