MVS Jan 2005.p65 - CBT Tape

the requirement to ship elements from the test LPARs, where
the development occurs, to the production LPARs, where the
applications actually run. One of the elements that is shipped
is the compile and link-edit listings that are stored by Endevor.
These are shipped so that if there is a production abend the
applications programmer can have the compile listing available
for debugging purposes. The compile listings are stored in a
compressed format, to save space. Endevor provides a utility
to read and expand the listing to human-readable format.
When we decided to make separate sysplexes, however, we
elected to license the use of Endevor only on our test sysplex.
This meant the listings that were shipped over to the production
sysplex would not be usable by the applications programmers
for debugging, because we were not licensed to run the
Endevor utility to expand the compressed listings on our
production sysplex. We decided to examine the listings and
found that we could easily write a utility to expand the listings
back to human-readable format ourselves, without the use of
any Endevor utility. This is the mechanism we decided to use
on the production sysplex.
It turns out that the compression method used by Endevor is
the replacement of repeating character strings with either a 2or
a 3-byte flag string. We found two different types of flag
string. The first was for the replacement of repeating blanks
with a 2-byte field. The first byte was a flag indicator byte
containing X'FD', followed by another 1-byte field that was the
repetition count. The second was for the replacement of
repeating non-blank characters with a 3-byte field. The first
byte was a flag indicator byte containing X'FC', followed by a
1-byte field containing the character that had been compressed,
followed by another 1-byte field containing the repetition
count.
With the above information, a rather simple REXX EXEC was
written to read a compressed listing file stored as a PDS
member, and to expand the flag fields back to their original
format. If the EXEC is called under ISPF, then ISPF browse is
invoked to display the listing, otherwise the user is given the
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