SET ISOLATION

Defines the transaction isolation level for the current connection.

Syntax

SET ISOLATION TO
  { DIRTY READ
  | COMMITTED READ [LAST COMMITTED] [RETAIN UPDATE LOCKS]
  | CURSOR STABILITY
  | REPEATABLE READ }

Usage

The SET ISOLATION instruction sets the transaction isolation level for the current connection. See database concepts in your database server documentation for more details about isolation levels and concurrency management.

When possible, the underlying database driver sets the corresponding transaction isolation level. If the isolation level cannot be set, the runtime system generates an exception.

When using the DIRTY READ isolation level, the database server might return a phantom row, which is an uncommitted row that was inserted or modified within a transaction that has subsequently rolled back. No other isolation level allows access to a phantom row.

On most database servers, the default isolation level is COMMITTED READ, which is appropriate to portable database programming.

The LAST COMMITTED and RETAIN UPDATE LOCKS options have been added to the language syntax for conformance with IBM^® Informix^® IDS 11. The LAST COMMITTED option can be turned on implicitly with a server configuration parameter, saving unnecessary code changes.

MAIN
  DATABASE stock
  SET ISOLATION TO COMMITTED READ
  ...
END MAIN