TRX-HOLDS-LOCKS - This configuration variable allows you to control which locks are released at the end of a transaction. If this variable is set to "1", then locks set using the READ statement that are not specifically released or replaced by extended transaction locks (for example, by a REWRITE) are held at the end of the transaction. Locks are released during a transaction by any operation that would ordinarily release them, unless those locks were replaced by extended transaction locks.
If TRX-HOLDS-LOCKS is set to "0" (the default), then locks are released at the end of a transaction, and the UNLOCK verb has no effect during a transaction.