JCL Optimization

• Use automatic block size (BLKSIZE=0) – requires block contains 0 records in the file definition of cobol programs, except for tape or cartridge (UNIT=CART) . For tape or cartridge set the blocksize as close to 32,000 bytes as possible. Reduces I/O , disk space, and cpu required to process the required I/O.
• When RECFM=VB, use a utility to calculate the best blocksize like TSO SPC-(SPC is a clist instaed of this write actual formula if required ) to get the best blocksize
  
• Use TRK instead of CYL or BLK parm whenever possible ( 1 CYL = 15 TRKS)
  
• Check if GDG’s are required, if yes check the optimize version number.
  
• Save large files ( > 200 CYL) on cartridge rather than DASD; use TRTCH=COMP with cartridge. 1 CYL = 15TRKS = ((56,664 bytes x 15) = .85 megabyte) . Based on the frequency and priority of batch run, decide to put files on DASD or Tape.
  200 CYL = 170 Megabyte. Cost per week = 170 x .09 = $15.30
  200 cyl on disk = 170MB cost $15.30 a week times 4 weeks per month = $61.20.
  1 Volume Cartridge tape = 400MB storage capacity on site cost per month $2.08 + $1.87 per tape mount = $3.95 per month for storage
  1 Volume Cartridge tape = 400MB storage capacity off site cost per month $0.26+ $1.87 per tape mount = $2.13per month for storage
  (The above mentioned rates may differ from site to site.)
  
• Space parm; after calculating the required consumption, the primary portion should be depending on the average no of records and secondary portion should be the largest possible out of the overall consumption., use RLSE option also to free up/reduce file space allocated when it not needed.
  
• Use ‘Refer Back’ option when writing to cartridge multiple times within a job
  
• Use disposition of delete if possible
• Use consistent high-level qualifiers and as few as possible
• Avoid to use in-stream data directly in the jcl, instead, use parmlib member.
• Use standard PROCs/JCLs, if available.