Final practice

/* REXX */
ARG volser ds method nds
/* CHECK FOR RENAME */
if (nds='' & method/='RENAME')|(nds/='' & method='RENAME') then
do
  CALL FIND
  SEQ=2+(SEQ-1)*3
/* THE GENERAL PART OF ALL CODES */
  queue "//a31job1  JOB A31,LEVIN,NOTIFY=&SYSUID,MSGCLASS=X"
  queue "//STEP01   EXEC PGM=ADRDSSU"
  queue "//SYSPRINT DD SYSOUT=*"
  queue "//FROM  DD DISP=SHR,UNIT=T1,VOL=SER="TAPE",LABEL=("SEQ",BLP)"
  /* PART OF THE'TEMP' METHOD*/
  IF method='TEMP' THEN
  DO
    queue "//TO       DD DISP=SHR,UNIT=SYSDA,VOL=SER=WORKTS"
    queue " RESTORE  DATASET(INCLUDE("DS"))-"
    queue " INDD(FROM) OUTDD(TO) TOLERATE(ENQFAILURE) -"
    queue " CANCELERROR ADMIN REPLACE"
    queue "$$"
    "submit * end($$)"
  END
   /* PART OF THE 'REPLACE' METHOD */
  ELSE
  IF method='REPLACE' THEN
  DO
    queue "//TO       DD DISP=SHR,UNIT=SYSDA,VOL=SER="VOLSER""
    queue " RESTORE  DATASET(INCLUDE("DS"))-"
    queue " INDD(FROM) OUTDD(TO) TOLERATE(ENQFAILURE) -"
    queue " CANCELERROR ADMIN REPLACE"
    queue "$$"
    "submit * end($$)"
  END
  /* PART OF THE 'RENAME' METHOD */
  ELSE
  IF method='RENAME' THEN
  DO
    IF SYSDSN("'"NDS"'")/='OK' THEN
    DO
      queue "//TO       DD DISP=SHR,UNIT=SYSDA,VOL=SER="VOLSER""
      queue " RESTORE  DATASET(INCLUDE("DS"))-"
      queue " INDD(FROM) OUTDD(TO) TOLERATE(ENQFAILURE) -"
      queue " CANCELERROR ADMIN RENAMEUNCONDITIONAL("DS","NDS") -"
      queue " CATALOG"
      queue "$$"
       "submit * end($$)"
     END
     /* NAME CHECK */
     ELSE
     SAY 'CHOOSE A DIFFERENT NAME,IT ALREADY EXISTS'
   end
 END
 else
 say 'invalid parameters'
 EXIT 0
 /* MAIN FIND PROC */
 FIND: PROCEDURE EXPOSE VOLSER TAPE SEQ
 /* FINDING VOLSER */
 /* cutting disk name */
 DSNLOG=SYSDSN("'SOFT.SUPPORT("VOLSER")'")
 /* CHECKING IF DISK NAME IS EXISTS IN SOFT SUPPORT */
 IF DSNLOG='OK' THEN
 DO
   "alloc da('SOFT.SUPPORT("VOLSER")') F(INPUT) shr reuse"
   "execio * diskr INPUT (stem VOL. finis"
   "FREE F(INPUT)"
   TAPE=SUBSTR(VOL.3,57,6)
   /* IF TEMP FILE(LIB1) IS EXISTS */
  /* THEN DELETE IT */
  if sysdsn("'LIB1'")='OK' THEN
  DO
  ADDRESS TSO "DELETE 'LIB1'"
  END
  /* LISTING OUT ALL FILES FROM THE TAPE: */
  "HSEND LIST DUMPVOLUME("TAPE") ODS('LIB1')"
  /* FINDING PROCESS */
  /* WAITING FOR PREVIOUS FREE F() */
  ADDRESS SYSCALL 'sleep 1'
  "alloc da('lib1') F(indd) shr reuse"
  "execio * diskr indd (stem strings. finis"
  "free f(indd)"
  /* P - VARIABLE FOR INCREMENTING STEMS AND CHECKING FIND RESULT */
  P=0
  DO I=1 TO STRINGS.0
  IF INDEX(STRINGS.I,' 'VOLSER' ') /= 0 THEN
    DO
      P=P+1
      STRS.0=P
      STRSFULL.0=P
      STRS.P=SUBSTR(STRINGS.I,25,3)
      STRSFULL.P=STRINGS.I
   END
 END
 IF P /= 0 THEN
 DO
   IF P>1 THEN
   DO
     /* SETTING UP 1ST LINE AS INITIAL YYYY/MM/DD */
     Y=SUBSTR(STRSFULL.1,50,4)
     M=SUBSTR(STRSFULL.1,55,2)
     D=SUBSTR(STRSFULL.1,58,2)
     SEQ=SUBSTR(STRSFULL.1,25,3)
     DO I=2 TO STRS.0
       IF SUBSTR(STRSFULL.I,50,4)>Y THEN
       DO
         Y=SUBSTR(STRSFULL.I,50,4)
         M=SUBSTR(STRSFULL.I,55,2)
         D=SUBSTR(STRSFULL.I,58,2)
         SEQ=SUBSTR(STRSFULL.I,25,3)
       END
       ELSE
       IF SUBSTR(STRSFULL.I,50,4)=Y THEN
       DO
         IF SUBSTR(STRSFULL.I,55,2)>M THEN
          DO
            M=SUBSTR(STRSFULL.I,55,2)
            D=SUBSTR(STRSFULL.I,58,2)
            SEQ=SUBSTR(STRSFULL.I,25,3)
          END
          ELSE
          IF SUBSTR(STRSFULL.I,55,2)=M THEN
          DO
            IF SUBSTR(STRSFULL.I,58,2)>D THEN
            DO
              D=SUBSTR(STRSFULL.I,58,2)
              SEQ=SUBSTR(STRSFULL.I,25,3)
            END
          END
        END
      END
      SEQ=2+(SEQ-1)*3
      /* SAY 'LAST DATE:'||Y||'/'||M||'/'||D||' */
      RETURN 1
    END
    ELSE
    DO
    SEQ=SUBSTR(STRSFULL.1,25,3)*1
    SEQ=2+(SEQ-1)*3
    RETURN 1
    END
  END
  ELSE
  EXIT 0
END
ELSE
DO
SAY VOLSER 'NOT FOUND ON SOFT.SUPPORT'
RETURN 0
END