Don, Was this using the old Formatted File System? The military used lots of this for awhile.
Lloyd --- On Sat, 12/19/09, Don Higgins <[email protected]> wrote: > From: Don Higgins <[email protected]> > Subject: Re: 360 programs on a z/10 > To: [email protected] > Date: Saturday, December 19, 2009, 7:24 AM > All > > ISAM was used at Florida Power for the customer master file > before VSAM > before DB2. Assembler subroutines were called by > COBOL to access the file > either sequentially or randomly and with or without > update. The initial reason > for using assembler was lack of variable length in COBOL > initially, but it was a > useful choice as it isolated the applicaiton from both > software and hardware > changes such as moving from data cell to pizza ovens > etc. Interestingly the > DB2 version implemented in 1995 used assembler > compression/decompression > to reduce network traffic by 50% > > Anyway I remember studying the channel programs used by > ISAM and > although they were designed to maximize I/O speed, they > were severely > hampered by the lack of VSAM CA/CI indexing which resulted > in exceedly long > sequential chains of overflow records which could runs for > hours if the file was > not unloaded and reloaded to restore evenly distributed > overflow track space. > > Don Higgins > [email protected] > > ---------------------------------------------------------------------- > 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 > ---------------------------------------------------------------------- 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
