Du kan använda PL/SQL så här.
DECLARE
CANNOT_DROP_LAST_PARTITION EXCEPTION;
PRAGMA EXCEPTION_INIT(CANNOT_DROP_LAST_PARTITION, -14758);
ts TIMESTAMP;
BEGIN
FOR aPart IN (SELECT PARTITION_NAME, HIGH_VALUE FROM USER_TAB_PARTITIONS WHERE TABLE_NAME = 'MY_TABLE') LOOP
EXECUTE IMMEDIATE 'BEGIN :ret := '||aPart.HIGH_VALUE||'; END;' USING OUT ts;
IF ts < SYSTIMESTAMP - INTERVAL '15' DAY THEN
BEGIN
EXECUTE IMMEDIATE 'ALTER TABLE MY_TABLE DROP PARTITION '||aPart.PARTITION_NAME|| ' UPDATE GLOBAL INDEXES';
EXCEPTION
WHEN CANNOT_DROP_LAST_PARTITION THEN
EXECUTE IMMEDIATE 'ALTER TABLE MY_TABLE SET INTERVAL ()';
EXECUTE IMMEDIATE 'ALTER TABLE MY_TABLE DROP PARTITION '||aPart.PARTITION_NAME;
EXECUTE IMMEDIATE 'ALTER TABLE MY_TABLE SET INTERVAL( INTERVAL ''1'' DAY )';
END;
END IF;
END LOOP;
END;