Table Locks

DB2 can use table locks only when segmented table spaces are involved in the process. Table locks are always associated with a corresponding table space lock.

The same types of locks are used for table locks as are used for table space locks. S , U , X , IS , IX , and SIX table locks can be acquired by DB2 processes when data in segmented table spaces is accessed. Table 23.1 describes the options available to DB2 for table locking. The compatibility chart in Table 23.3 applies to table locks as well as table space locks.

For a table lock to be acquired, an IS -lock must first be acquired on the segmented table space in which the table exists. The type of table lock to be taken depends on the LOCKSIZE specified in the DDL, the bind parameters chosen for the plan being run, and the type of processing requested . Table 23.4 is a modified version of Table 23.2, showing the initial types of table spaces and table locks acquired given a certain set of conditions. Table locks are not acquired when the LOCKSIZE TABLESPACE parameter is used.

Table 23.4. How Table Locks Are Acquired

Type of Processing	LOCKSIZE	Isolation	Table Space Lock Acquired	Table Lock Acquired
MODIFY	ANY	CS	IS	IX
MODIFY	PAGE	CS	IS	IX
MODIFY	TABLE	CS	IS	X
MODIFY	ANY	RR	IS	X
MODIFY	PAGE	RR	IS	X
MODIFY	TABLE	RR	IS	X
SELECT	ANY	CS	IS	IS
SELECT	PAGE	CS	IS	IS
SELECT	TABLE	CS	IS	S
SELECT	ANY	RR	IS	S
SELECT	PAGE	RR	IS	S
SELECT	TABLE	RR	IS	S