Re: Optimal Tape Blocksize

From: "Gibney, Dave" <gibney@xxxxxxx>

Still, why worry about details the system will handle for you.

I agree 100%. I told our programmers long ago to stick to
BLKSIZE=0 *and* DSORG=PS for datasets on DASD. This always work
(BLKSIZE close to half track).

Behalf Of Ted MacNEIL
On tape, it's as close to the maximum as possible.

I thought BLKSIZE=0 would also let the system choose the optimal bloksize
for datasets on tape. I'm starting to review datasets on tape the way Lizette
is doing, and I can see that in some cases the chosen bloksize is really poor.
(i.e. RECFM=FB,LRECL=22,BLKSIZE=0 in jcl, but I see BLKSIZE=4620 under DFSMSrmm)

In my DEVSUPxx I have only coded COMPACT=YES.

I can't understand why such poor BLKSIZE are chosen. I would really appreciate
if anyone could shed some light on this.

TIA

Walter Marguccio
z/OS Systems Programmer
BELENUS LOB Informatic GmbH
Munich - Germany




----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to listserv@xxxxxxxxxxx with the message: GET IBM-MAIN INFO
Search the archives at http://bama.ua.edu/archives/ibm-main.html
.

Relevant Pages

  • Re: z/OS 1.9 Features summary
    ... form, supplying a valid but nonoptimal BLKSIZE, in OS/360 ... Maybe you don't recall, but even with Virtual Storage Constraint, and system programmers evaluating which modules could be eliminated from processor storage so that demands could be met in CSA or Private ... ... For IBM-MAIN subscribe / signoff / archive access instructions, ...
    (bit.listserv.ibm-main)
  • Re: Optimal Tape Blocksize
    ... I told our programmers long ago to stick to ... I can't understand why such poor BLKSIZE are chosen. ... For IBM-MAIN subscribe / signoff / archive access instructions, ... send email to listserv@xxxxxxxxxxx with the message: GET IBM-MAIN INFO ...
    (bit.listserv.ibm-main)
  • Re: Displaying HOLDDATA on an already received tape
    ... LRECL and BLKSIZE for the tape. ... For IBM-MAIN subscribe / signoff / archive access instructions, ... send email to listserv@xxxxxxxxxxx with the message: GET IBM-MAIN INFO ...
    (bit.listserv.ibm-main)
  • Re: Calculate Tape Bytes to Tracks
    ... tape datasets could go on dasd. ... I am using CA1 to get the LRECL, BLKSIZE and BLKCNT to determine how many ... there has been reported conditions where a BLKSIZE is not reported to ... For IBM-MAIN subscribe / signoff / archive access instructions, ...
    (bit.listserv.ibm-main)
  • Re: recommended way to send large files from Z/os to WIN and backward
    ... MFNetDisk can emulate 3490 tape without real tape and with automatic fast ... PC can be Linux or Windows. ... For IBM-MAIN subscribe / signoff / archive access instructions, ... send email to listserv@xxxxxxxxxxx with the message: GET IBM-MAIN INFO ...
    (bit.listserv.ibm-main)