system.db.beginNamedQueryTransaction( project, database, [isolationLevel], [timeout])
String project - The name of the project that contains the named query.
String database - The name of the database connection to create a transaction in.
Integer/Constant isolationLevel - The transaction isolation level to use. Use one of the four constants: system.db.READ_COMMITTED, system.db.READ_UNCOMMITTED, system.db.REPEATABLE_READ, or system.db.SERIALIZABLE. If omitted, uses system.db.READ_COMMITTED
Long timeout timeout - The amount of time, in milliseconds, that this connection is allowed to remain open without being used. Timeout counter is reset any time a query or call is executed against the transaction, or when committed or rolled-back. If omitted, defaults to 30,000.
String - The new transaction ID. You'll use this ID as the "tx" argument for all other calls to have them execute against this transaction.
Gateway, Perspective Session