All of the standard rules of COBOL apply in multiple-record mode, with
the following limitations:
- Only files that require no record locking can be opened in
multiple-record mode. This limitation is enforced silently on both the client
and the server. If a user tries to open a file that requires record locking in
this mode, the file is still opened, but not in multiple-record mode. In other
words, multiple-record mode does not affect the lock mode specified by the
COBOL program, but the lock mode may affect whether records are sent in single
or multiple-record packets.
- Files open in this mode may not be read backward. (that is,
READ-NEXT commands are supported; READ-PREVIOUS commands are not.) The purpose
of this mode is to improve sequential performance. If you attempt to read a
file backward that has been opened in multiple-record mode, an error 9B results
(requested operation is not supported).