ca.portal.admin

Re:Re: Maximum Page Size for IDMS Database Files

Discussion created by ca.portal.admin on Jul 18, 2006
Dusting off the cobwebs from my brain I seem to remember that the 32K
restriction was in the I/O subsystem. When an access method, like BDAM or
QSAM, built EXCP commands the op codes, address, flag bytes and byte count
were placed into a channel command word (CCW) which was actually two words
long. In the original (format-0) version the data address was limited to 24
bytes so all I/O was placed below he line. Later in the format-1 version of
the CCW the address field was opened up to 31 bits so I/O could go directly
above the line. However, in both formats the byte count field would only
support 32k.

I believe (but not positive) that there is now a format-2 CCW which can
obtain a larger byte count. So if the hardware device supports larger
blocks, the access method has been updated to use the format-2 CCWs, and the
IDMS internal software and control blocks can support the larger pages; then
you should be good to go. But that is a few ifs.

Bill Boyce
GE Money

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