我想在捕获异常后回滚数据，但它没有生效。
我的存储过程如下：

CREATE OR REPLACE PROCEDURE CLEAN_YQCALLSDR (
    saveMonths IN INTEGER, ret OUT VARCHAR2 ) AS
BEGIN
    ret := 0;
        FOR rec IN (SELECT partition_name, high_value FROM user_tab_partitions WHERE table_name = 'a')
        LOOP
            IF to_date(substr(rec.high_value, 11, 10), 'yyyy-mm-dd') BETWEEN add_months(SYSDATE, -24) AND add_months(SYSDATE, -saveMonths) THEN
                                 execute IMMEDIATE 'ALTER TABLE a DROP PARTITION ' || rec.partition_name;
                -- Artificially created anomalies
                                ret := ret/0;
            END IF;
        END LOOP;
    EXCEPTION
        WHEN OTHERS THEN
            -- 回滚事务
            DBMS_OUTPUT.put_line('sqlcode : ' || sqlcode);
            DBMS_OUTPUT.put_line('sqlerrm : ' || sqlerrm);
            ret := 1;
            ROLLBACK;
END;

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