The following table lists the associations between individual SQL DML statements and lock upgrades and downgrades at the row (rowkey or rowhash), view, base table, and database object levels:
| LOCKING Modifier Severity | SQL DML Statements |
|---|---|
| EXCLUSIVE or WRITE |
|
| READ or SHARE | SELECT |
| ACCESS | SELECT |
| ACCESS for LOAD COMMITTED | SELECT |
EXCLUSIVE and WRITE are the only lock severities for the DELETE, INSERT, MERGE, UPDATE, and SELECT AND CONSUME statements, because the default lock severity for these statements is WRITE. You cannot downgrade a WRITE lock for these statements. Because the SELECT statement does not change data, and therefore cannot compromise database integrity, you can change its default locking severity to any other severity.
If you specify locking severity levels lower than those in the preceding table, the system uses WRITE.
For details about locking levels, locking severities, and the relationship between them, see Database Locks, Two-Phase Locking, and Serializability.