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