File status 37: OPEN mode not supported by the file

What it means

Status 37 is a permanent error from OPEN. The file exists and is allocated, but the open mode doesn't match what the file can do. IBM lists three cases. OPEN OUTPUT or EXTEND on a file that can't be written. OPEN I-O on a file that doesn't support both reading and writing. OPEN INPUT on a file that can't be read.

It mostly concerns QSAM files, because the DD decides what the file can do. Updating records in place with OPEN I-O and REWRITE needs a direct access device, so a QSAM file on tape can't be opened I-O. In-stream data (DD *) can only be read and a SYSOUT data set can only be written, so opening one of them the other way round can also end in 37.

Under the older CMPR2 behavior these cases were reported as 90, so old programs that test for 90 may miss a 37. If the program has no FILE STATUS clause and no error declarative, the runtime issues IGZ0035S and the program ends with abend U4038.

Common causes

• OPEN I-O on a QSAM file on tape, or on another device that can't rewrite records in place.
• Opening in-stream data (DD * or DD DATA) for OUTPUT or EXTEND, or a SYSOUT data set for INPUT. These only work in one direction, and the OPEN fails, often with 37.
• The program's open mode was changed, for example from INPUT to I-O to add an update, without changing the JCL.

How to find the problem

1. DISPLAY the status after OPEN, or read the IGZ0035S message, which names the file.
2. Look at the DD for that ddname in the JESJCL listing. Note whether it's DD *, SYSOUT, a tape or a disk data set.
3. Find the OPEN statement in the program and the mode it uses.

How to fix it

• Match the mode to the device. Use a disk data set for files that need OPEN I-O.
• Write reports and work output to SYSOUT or a data set, and read control cards from DD *, not the other way round.
• If a program has to update a tape file, copy it to disk, update it there, and copy it back.
• Add a FILE STATUS clause and check it after OPEN, so a 37 is reported with the file name.

Last reviewed 2026-10-18 by the WND Software team. Written in our own words. For the full reference, check IBM’s Enterprise COBOL documentation for your release.