Default Isolation Levels

The default isolation level for a particular database is established when you create the database according to database type. The following list describes the default isolation level for each database type.

Isolation Level
Database Type
Dirty Read
Default level in a database without logging
Committed Read
Default level in a logged database that is not ANSI compliant
Repeatable Read
Default level in an ANSI-compliant database
The default level remains in effect until you issue a SET ISOLATION statement. After a SET ISOLATION statement executes, the new isolation level remains in effect until one of the following events occurs:
  • You enter another SET ISOLATION statement.
  • You open another database that has a default isolation level different from the level that your last SET ISOLATION statement specified.
  • The program ends.

For a HCL OneDB™ database that is not ANSI-compliant, unless you explicitly set the USELASTCOMMITTED configuration parameter, the LAST COMMITTED feature is not in effect for the default isolation levels. The SET ENVIRONMENT statement or the SET ISOLATION statement can override this default and enable LAST COMMITTED for the current session.