VSAM file status 22 duplicate key

VSAM file status 22: Duplicate key — WRITE tried to add a record whose key already exists.

What it means

• Duplicate key — WRITE tried to add a record whose key already exists.
• Sequence error on a sequential WRITE.

Common causes

• Restart reprocessing inserting the same records.
• Key not unique in input data.
• ESDS written with keys out of order.

How to diagnose

• Find the duplicate key value.
• Check restart logic for repeated inserts.

How to fix it

• Skip duplicates, or delete-then-insert where appropriate.

Example: Always check FILE STATUS after I/O

FILE STATUS after every I/O turns mystery failures into clear codes.

Interview tip

• Q: How would you troubleshoot a VSAM file status 22 duplicate key in production?
• A: I would confirm the exact file status code, check the JCL DD and catalog, then apply the specific fix.

Prevention checklist

• Check FILE STATUS after every OPEN/READ/WRITE.
• Keep FD layouts in sync with cluster definitions.