Enable/Disable the dbms_jobs

First get the job number and status of dbms_jobs:
N – Means enable , Y- means disable

     jobno SCHEMA_USE B
---------- ---------- -
WHAT
-------------------------------------------------------------------------------
         1 HR         N
INSERT INTO employees VALUES (7345, 'RAM',
   'SHARMA', 'ram@orcl.com', NULL, SYSDATE, 'AP', NULL,
    NULL, NULL, NULL);

Disable the job

EXEC DBMS_IJOB.BROKEN(jobno,TRUE);

Enable a job

EXEC DBMS_IJOB.BROKEN(jobno,FALSE);

REMOVE A DBMS_JOBS

EXEC DBMS_IJOB.remove(jobno) ;