ABAP Program for Limit the parallel instances a particular heavy batch job can have

REPORT ZIMRE000.
************************************************************************
* This program limits the number of parallel instances a particular
* heavy batch job (JOB_NAME) can have.
* The program has to be scheduled as the first step of a job, while the
* heavy batch job should be the second step. The first step (this
* program) checks the number of jobs already running, and if it is
* over the limit (MAX_NUM) it reschedules itself to run in X minutes
* (X selected by a radiobutton), and then aborts. A variant with
* the corresponding MAX_NUM, X and JOB_NAME has to be created before
* scheduling the job.
* To prevent a deadlock (too many batch job start at the same time, and
* they think that there are already many jobs running, and they are
* rescheduling themselves to run again X time later - causing the same
* situation again) X is varied by a random +/- 1 minute.
************************************************************************
TABLES: TBTCO.
SELECTION-SCREEN BEGIN OF BLOCK BLK WITH FRAME.
SELECTION-SCREEN BEGIN OF LINE.
SELECTION-SCREEN COMMENT 1(40) A.
PARAMETERS: JOB_NAME(30).
SELECTION-SCREEN END OF LINE.
SELECTION-SCREEN BEGIN OF LINE.
SELECTION-SCREEN COMMENT 1(40) B.
PARAMETERS: MAX_NUM TYPE N.
SELECTION-SCREEN END OF LINE.
SELECTION-SCREEN COMMENT /1(50) C.
PARAMETERS: 5_MIN RADIOBUTTON GROUP PERI,
10_MIN RADIOBUTTON GROUP PERI,
30_MIN RADIOBUTTON GROUP PERI,
1_HOUR RADIOBUTTON GROUP PERI,
2_HOURS RADIOBUTTON GROUP PERI,
4_HOURS RADIOBUTTON GROUP PERI,
8_HOURS RADIOBUTTON GROUP PERI.
SELECTION-SCREEN END OF BLOCK BLK.
*
INITIALIZATION.
A = 'THE NAME OF THE BACH JOB:'.
B = 'MAXIMUM NUMBER OF CONCURRENT BATCH JOBS:'.
C = 'RESTART IN:'.
*
START-OF-SELECTION.
DATA: COUNTER TYPE I.
DATA: UZENET(40).
DATA: DATUM TYPE D, TIME TYPE T.
DATA: NEW_DATUM TYPE D, NEW_TIME TYPE T.
DATA: AMOUNT TYPE T.
DATA: NEW_JOBHEAD LIKE TBTCJOB.
DATA: T TYPE I.
* Some preparations
IF 5_MIN = 'X'.
AMOUNT = 300.
ELSEIF 10_MIN = 'X'.
AMOUNT = 600.
ELSEIF 30_MIN = 'X'.
AMOUNT = 1800.
ELSEIF 1_HOUR = 'X'.
AMOUNT = 3600.
ELSEIF 2_HOURS = 'X'.
AMOUNT = 7200.
ELSEIF 4_HOURS = 'X'.
AMOUNT = 14400.
ELSEIF 8_HOURS = 'X'.
AMOUNT = 28800.
ENDIF.
*
GET RUN TIME FIELD T.
GET TIME.
DATUM = SY-DATUM.
TIME = SY-UZEIT.
TIME = TIME + AMOUNT.
IF TIME < dialog="N" source_jobcount="TBTCO-JOBCOUNT" source_jobname="TBTCO-JOBNAME" target_jobname="TBTCO-JOBNAME" new_jobhead="NEW_JOBHEAD" cant_enq_job="9."> 9. EXIT. ENDIF.
ENDDO.
*
CALL FUNCTION 'JOB_CLOSE'
EXPORTING
JOBNAME = NEW_JOBHEAD-JOBNAME
JOBCOUNT = NEW_JOBHEAD-JOBCOUNT
SDLSTRTDT = DATUM
SDLSTRTTM = TIME.
* Abort the second step
UZENET = 'It is not ERROR! Rescheduling!'.
MESSAGE ID '00' TYPE 'A' NUMBER '208' WITH UZENET.
ENDIF.