Informix CLOSE – PB Docs 2022

If a database stored procedure returns a result set, it must be
closed when processing is complete.

Closing a procedure looks the same as closing a cursor:

As with cursors, if a procedure executes successfully and returns at
least one result set and is not closed, a result set is pending and no SQL
commands other than the FETCH can be executed. Procedures with result sets
should be closed as soon as possible.

The procedure remains open until you close it, execute a COMMIT or a
ROLLBACK, or end the database connection.