Do I need to COMMIT in a COBOL batch DB2 program?

Updated a bunch of rows in a loop. Program ended fine. Did DB2 save them automatically or did I forget something important?

Batch usually needs explicit COMMIT (or your shop framework does it). If you never commit and the job ends without one, behavior depends on how the connection closes - do not rely on luck.

Also commit every N rows on big updates so you do not hold locks forever.

Ask your team for the standard commit pattern. Some shops wrap it in a copybook paragraph.