read-only-clause
The read-only clause specifies that the result table is read-only. Therefore, the cursor cannot be referred to in positioned UPDATE or DELETE statements.
read-only-clause
Some result tables are read-only by nature (for example, a table based on a read-only view.) FOR READ ONLY can still be specified for such tables, but the specification has no effect.
For tables in which updates and deletes are allowed, specifying FOR READ ONLY can possibly improve the performance of FETCH operations as DB2® can do blocking and avoid exclusive locks. For example, in programs that contain dynamic SQL statements without the FOR READ ONLY or ORDER BY clause, DB2 might open cursors as if the UPDATE clause was specified.
A read-only result table must not be referred to in an UPDATE or DELETE statement, whether it is read-only by nature or specified as FOR READ ONLY.
To take advantage of the possibly improved performance of FETCH operations while guaranteeing that selected data is not modified and preventing some types of deadlocks, you can specify FOR READ ONLY in combination with the optional syntax of USE AND KEEP ... LOCKS on the isolation-clause.
Alternative syntax and synonyms: FOR FETCH ONLY can be specified as a synonym for FOR READ ONLY.