SET LOCK MODE

Defines the behavior of the program that tries to access a locked row or table.

Syntax

SET LOCK MODE TO { NOT WAIT | WAIT[ seconds ] }

seconds defines the number of seconds to wait for lock acquisition.

Usage

The SET LOCK MODE instruction defines the timeout for lock acquisition for the current connection.

When possible, the underlying database driver sets the corresponding connection parameter to define the timeout for lock acquisition. But some database servers may not support setting the lock timeout parameter. In this case, the runtime system generates an exception.

When using the NOT WAIT clause, the timeout is set to zero. If the resource is locked, the database server ends the operation immediately and raises an exception with the SQL error.

When using the WAIT clause with a number of seconds, if the resource is locked, the database server waits for the specified seconds, and then raises an exception with an SQL error.

When using the WAIT clause without a number of seconds, the database server waits for lock acquisition for an infinite time.

With most database servers, the default is to wait for locks to be released.

Make sure that the database server and corresponding database driver both support a lock acquisition timeout option, otherwise the program will raise an exception.

Example

MAIN
  DATABASE stock
  SET LOCK MODE TO WAIT 20
  ...
END MAIN