On Wed, 5 Jul 2006 09:43:21 -0600, Paul Gilmartin <[EMAIL PROTECTED]> wrote:
>In a recent note, Tom Marchant said: > >> Date: Wed, 5 Jul 2006 10:29:18 -0500 >> >> >> In the case of RECFM=VBA, LRECL=137, BLKSIZE=27998 (SDB), one might >> >> assume an average unused space at the end of each block to be 1/2 >> >> of 137. 69 bytes out of 27,998 bytes is about 0.25%. >> >> >> >I don't understand "unused space at the end of each block". Surely >> >the interblock gap isn't larger by that amount, so the unused space >> >must exist within the block. The only way I know this can occur is >> >if RECFM=VBS and the block ends with a null segment. I don't believe >> >this is commonly done. >> > >> Sorry, I didn't say that clearly. I meant that when a short block >> is written, the amount of unused space at the end of the track will >> increase by the difference between BLKSIZE and the length of the >> block actually written. >> >However, if enough short blocks are written, the "unused" space >may accumulate to enough to contain an entire block, and the short >block may cause the unused space to actually decrease. > Maybe, but that would be unusual, and it would be more likely with a small blocksize, which doesn't efficiently use the space on the track. If we had support for 64KB tracks, we would probably go back to full track blocking. In that case, there would not be enough space left on the track to hold the next redord. >FBA rules. That depends upon how it would work. Would each block start immediately after the last, or at the beginning of the next physical block? What about crossing extents? How would a PDS work, or anything else that uses TTR (or MBBCCHHR)? Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
