25003ERRORTier 2 — Caution✅ HIGH confidence

inappropriate access mode for branch transaction

Category: Invalid Transaction StateVersions: All Postgres versions

What this means

SQLSTATE 25003 is raised when the access mode (READ ONLY vs READ WRITE) specified for a transaction does not match the access mode required by the branch transaction or the current connection state.

Why it happens

1Attempting to change the transaction access mode in a way that conflicts with the current session or branch transaction state

How to reproduce

Setting READ WRITE mode in a READ ONLY transaction.

trigger — this will ERROR

ERROR: inappropriate access mode for branch transaction

Fix 1: Set the correct transaction access mode before starting the transaction

When branch transaction access mode conflicts occur.

fix

BEGIN READ WRITE; -- or READ ONLY

Why this works

Specify the access mode at transaction start rather than attempting to change it mid-transaction.

Sources

📚 Official docs: https://www.postgresql.org/docs/current/errcodes-appendix.html

🔧 Source ref: Class 25 — Invalid Transaction State

Confidence assessment

✅ HIGH confidence

Standard SQLSTATE. Stable across versions.