Microsoft® SQL Server™ 2000 Unleashed, Second Edition

Lock Compatibility

If a process has already locked a resource, the granting of lock requests by other transactions on the same resource is governed by the lock compatibility matrix within SQL Server. Table 38.5 shows the lock compatibility diagram for the SQL Server Lock Manager, indicating which lock types are compatible and which lock types are incompatible when requested on the same resource.

Table 38.5. SQL Server Lock Compatibility Matrix

		Existing Lock Type
Requested Lock Type	IS		S	U	IX	SIX	X	Sch-S	SCH-M	BU
Intent Shared	Yes		Yes	Yes	Yes	Yes	No	Yes	No	No
Shared	Yes		Yes	Yes	No	No	No	Yes	No	No
Update	Yes		Yes	No	No	No	No	Yes	No	No
Intent Exclusive	Yes		No	No	Yes	No	No	Yes	No	No
Shared with Intent Exclusive	Yes		No	No	No	No	No	Yes	No	No
Exclusive ...