Walter, > > 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. > As Kees noted, the program could have a blocksize in imbedded which overrides anything from the label and jcl. Another way for a program to override the blocksize is to include a dcb exit to set the blocksize. Unlikely but possible if you do not find a hardcoded blocksize in the dcb in the program. Regards, John
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