The TransIsolation property behavior of the PSQL Direct Access Components is different from that of their Embarcadero equivalents.
Use the property TPvDatabase.TransIsolation to specify the transaction isolation level for the database.
PSQL Direct Access Components only support the tiReadCommitted mode. This means that other users cannot see the changes made to a file until the transaction ends. This is the only setting supported by the PSQL database engine.