Microsoft® SQL Server 2008 R2 Unleashed

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 37.3 shows the lock compatibility matrix for the locks most commonly acquired by the SQL Server Lock Manager, indicating which lock types are compatible and which lock types are incompatible when requested on the same resource.

Table 37.3 SQL Server Lock Compatibility Matrix

For example, if a transaction has acquired a shared lock on a resource, the possible lock types that can be acquired on the resource by other transactions are intent shared, ...