SQLCODE -803 duplicate key

SQLCODE -803: duplicate key — INSERT hit an existing unique key value.

What it means

• After every EXEC SQL, DB2 returns a SQLCODE: 0 means success, +100 means no row found, and negative values mean an error.

Common causes

• Program inserts a row whose key already exists.
• Restart reprocessing inserted rows twice.

How to diagnose

• Identify the duplicate key value from SQLERRM.
• Check whether the row genuinely exists already.

How to fix it

• Skip existing rows, or change to UPDATE logic.
• Fix restart logic so inserts are not repeated.

Example: Make inserts idempotent

-803 often means the work is already done.

Interview tip

• Q: How would you troubleshoot a SQLCODE -803 duplicate key in production?
• A: I would check the SQLCODE and SQLERRM immediately after the failing statement, reproduce in SPUFI, then apply the specific fix.

Prevention checklist

• Always check SQLCODE after every EXEC SQL statement.
• Log the SQLCODE, SQLSTATE and failing statement for support.