It is my recollection that, pretty much since the advent of buffered tape drives (e.g. 3590, 9840,... ) the actual blocksize written to tape is independent of what is specified in the JCL.
In other words, it does not matter what you code in JCL, the actual data block written to physical tape will be a hardware determined value. I believe Lizette's suggestion of using TAPETOOL is a good one, My $0.02 USD worth, <snip> > First I need thank you who replied to my question. > I should introduce my problem's background and my concern. > The tape is virutal tape of oralce, vsm5. > I am backing up extended format PS dataset to VSM5 using ADRDSSU. > I tested using dss to backup, no matter what block size I specified in > JCL, ADRDSSU will report same number of blocks in message IEC205I. > And the backup speed will also be same no matter what block size I > specified in JCL. > Here is my testing result: > st_TIME end_TIME backup source data type VOLSER VTV > size(mb) VTV size(comp)(mb) tape block size(KB) Total block > count > reported by DSS backup speed(MB/S) > 11:31:41 11:33:12 Extended format compressed AB3968 > 1854.15 647.77 128 33879 20.38 > 11:33:12 11:34:42 Extended format compressed AB3974 > 1854.15 647.77 64 33879 20.60 > 11:34:42 11:36:17 Extended format compressed AB3976 > 1854.15 647.77 256 33879 19.52 > > But this is not true for BASIC PS dataset, for basic PS dataset, I > did a similar > testing: > st_TIME end_TIME backup source data type VOLSER VTV > size(mb) VTV size(comp)(mb) tape block size(KB) Total block > count > reported by DSS backup speed(MB/S) > 13:08:07 13:11:37 Basic PS AB4075 6273.86 360.15 > 128 49117 29.88 > 13:11:37 13:16:00 Basic PS AB4078 6274.57 367.9 > 64 98426 23.86 > 13:16:00 13:19:04 Basic PS AB4082 6273.51 355.52 > 256 24528 34.10 </snip> ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
