Or just code: SPACE=(500,(10,2),RLSE), AVGREC=K
and let the system calculate how many tracks it needs. -----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Sri h Kolusu Sent: Wednesday, November 23, 2022 1:29 PM To: [email protected] Subject: Re: Bytes in a 3390 track >> How do I calculate the amount of space a ____ dataset needs? A 3390-n device has a capacity of 56,664 bytes per track, of which 55,996 bytes are accessible by applications programmers. The largest blocksize you can define is 32,760, which is good for tapes,but it is mere waste on DASD, as 55,996 - 32760 = 23,236 bytes left over, and because tracks can't be shared between other files, that leftover space would just be wasted. So, 55,996/2 = 27,998, which is half-track blocking, the most space-efficient blocksize to use on 3390's.If you have 3380 device types in your shop, the maximum half-track blocksize is 23,476. To calculate the most efficient blocksize to use: Optimal blocksize = INTEGER(half-track-blocksize/LRECL)*LRECL Assuming LRECL=500, so the optimal blocksize will be Integer(27,998/500) is 55 55 multiplied by lrecl(500) gives you 27500 which is the optimum blksize. On a 3390, the best blocksize for a QSAM (Queued Sequential Access Mode) file of record length 500 is 27,500.This will allow 55 records per block, or 110 records per track, or 1650 records per cylinder (cylinders are 15 tracks). Assuming your volume of records e is 10,000, you can fit that data in less than 7 cylinders(10,000/1650 = 6.06 rounded to 7) We allocate the primary space as 7 cylinders. Now the secondary space allocation is 20% of primary space which in this case is 7 * 0.2 = 1.4 rounded to 2 So, your space allocation for a dataset of lrecl 500 and a volume of 10,000 records would be SPACE=(CYL,(7,2),RLSE) Thanks, Kolusu ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
