In oracle 12 cr1 has built a timing to start the JOB, start is to set the END_DATE, but perform at half time, through the command, the END_DATE emptied,
Expect this job, it is should be able to run forever, but still in the original set the timing of the END_DATE stopped, the log information is a tiny="End time reached,"
Then job Enabled became false

If at this time in PLSQL developer shall be Enabled to enforce is set to true, the job will stop, after also performs a

But if you wait until the next day, to set the Enabled is set to true, the job will start, then run forever,

Don't know whether this is a question of setting or ORACLE problems?

Create a JOB code
The BEGIN
SYS. DBMS_SCHEDULER. CREATE_JOB (JOB_NAME=& gt; 'JOB_3357'
JOB_TYPE=& gt; 'STORED_PROCEDURE'
JOB_ACTION=& gt; 'PROD_TEST'
The START_DATE=& gt; To_date (' 2019-05-05 11:03:00,
'- dd yyyy - mm hh24: mi: ss'),
REPEAT_INTERVAL=& gt; 'the FREQ=SECONDLY; The INTERVAL=30 ',
END_DATE=& gt; To_date (' 2019-05-05 12:00:00,
'- dd yyyy - mm hh24: mi: ss'),
AUTO_DROP=& gt; FALSE,
COMMENTS=& gt; Null);
END;

The begin
Sys. Dbms_scheduler. The enable (name=& gt; 'JOB_3357');
end;


Empty END_DATE code
The BEGIN
SYS. DBMS_SCHEDULER. SET_ATTRIBUTE (' JOB_3357 ', 'END_DATE', ');
END;



In addition, empty END_DATE code, used to_date (null), effect is the same