Locks and Concurrency
A DELETE statement sets a WRITE lock for the table, partitions, or row. For a nonconcurrent load isolated delete operation on a load isolated table, the delete operation sets an EXCLUSIVE lock.
For a SELECT subquery, the lock depends on the isolation level for the session, the setting of the AccessLockForUncomRead DBS Control field, and whether the subquery is embedded within a SELECT or DELETE statement.
Transaction Isolation Level |
DBS Control AccessLockForUncomRead Field Setting |
Default Locking Severity for Outer SELECT and Ordinary SELECT Subquery Operations |
Default Locking Severity for SELECT Operations Embedded Within an UPDATE Request |
SERIALIZABLE |
FALSE |
READ |
READ |
TRUE |
READ |
||
READ UNCOMMITTED
|
FALSE |
READ |
|
TRUE |
ACCESS |