Default isolation level for new transactions.
At a glance
| Property | Value |
|---|---|
| Parameter | default_transaction_isolation |
| Category | Client Defaults |
| Default | read committed |
| Value type | boolean / enum / numeric |
| Change scope | Per-session (SET) |
What it does
The isolation level assigned to transactions that do not set one explicitly: read committed, repeatable read, or serializable.
How to apply a change
Can be set per session with SET, per role/database with ALTER ROLE/DATABASE ... SET, or globally in postgresql.conf.
Inspect the current value and source with SHOW default_transaction_isolation; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'default_transaction_isolation';.
Tuning guidance
Keep read committed for general OLTP. Use serializable where you need full anomaly protection and are ready to retry SQLSTATE 40001 serialization failures.