isolation level - cheeyoung/sqlplus-public GitHub Wiki

isolation level	Oracle	PostgreSQL
READ UNCOMMITTED	X	X	treated as READ COMMITTED in PostgreSQL
READ COMMITTED	default	default
REPEATABLE READ	X	O
SERIALIZABLE	O	O

Reference

SET TRANSACTION (21)

ISOLATION LEVEL Clause

SET TRANSACTION (15)

... In PostgreSQL READ UNCOMMITTED is treated as READ COMMITTED.