The returned value is APS_ID of a deleted phrase set if positive or an error code if negative. A phrase set can not be deleted while used by some advertiser (as described here).
SQL>select ANN_PHRASE_CLASS_ADD ('simple test', null, null, null, '123', '', 'dba', 'dba'); callret INTEGER _______________________________________________________________________________ 1 1 Rows. -- 0 msec. SQL>select ANN_PHRASE_CLASS_DEL ('simple test', 'dba', 'dba'); callret VARCHAR _______________________________________________________________________________ 1 1 Rows. -- 70 msec.