DUCK YES, Sri, DUCK YES!. I am here for this excellent content.
- KB ------- Original Message ------- On Thursday, November 24th, 2022 at 12:59 AM, Sri h Kolusu <[email protected]> wrote: > > > 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
