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+====== The Programmer's Exchange (PX) - A Review=====
+^Published By^Date^Version^Knowledge Level^Keywords^
+|Sprezzatura Ltd|01 JUL 1992|2.12+|EXPERT|PX|
+==== Introduction. ====
+If you've ever had to produce an update diskette for a remote system and
+found yourself struggling to remember which programs have been changed and
+which indexes have been added, then PX could be the utility for you. It's
+one of those "I must write one of these myself" tools that you somehow never
+seem to find the time for. Now Harmacek Data Systems have done the work for
+you with a utility which has been tried and tested in the field and proved
+to be so useful that they've now decided to share it with the rest of us
+(for a small cost, of course...)
+==== Product Description. ====
+The Programmer's Exchange is a tool which tracks amendments to any file in
+an AREV application. It has two main components: firstly, an MFS which is
+placed on all files to be monitored (including dictionaries) which generates
+audit records whenever a write or delete operation is encountered; and
+secondly, a suite of programs which allow a transmission file to be created
+from the audit of changes. This file can then be sent via diskette or modem,
+and is uploaded by another process at the remote site, applying the changes
+automatically. During the upload process, indexing information can be
+ignored simply by setting a command line flag if required.
+Other features include the ability to report on transactions already held,
+and to toggle the auditing MFS on and off. Since this is achieved using TCL
+commands (e.g. PX SUSPEND) it can easily be interfaced with any R/Basic
+programs.
+==== Installation and Use. ====
+PX comes on a single diskette, and it has a comprehensive user manual
+provided (in fact, given its target market it's almost too comprehensive in
+places). The manual is generally helpful and easy to follow, although
+personally I would have put the large bold-type warning message about not
+using the DOS copy command at the beginning instead of tucking it away on
+the last page.
+The installation is composed of two phases. Firstly, the software is loaded
+via a simple collector window process. Since PX is designed to work across
+accounts and applications the installation process defaults to the VERBS and
+COMMANDS files, although this can be overridden if required. I found only
+one glitch during this process when a W504 error message (The DICT.PX file
+on the REVBOOT volume is not available...) appeared. After acknowledging the
+message, the system recovered of its own accord and carried on to a
+successful completion - or so it appeared.
+The second installation phase is to apply the MFS to all the necessary files
+in an application. N.B. PX does not itself order the MFS chain if other
+MFS's are already present. The manual provides step by step instructions on
+how this can be achieved, but it necessarily assumes that the user will know
+the implications of ordering certain MFS's in certain ways. Again this
+process needs to be repeated once for each application. A collector window
+allows the user to select a volume and file list. Judicious use of a
+pre-tagged multiple selection popup to highlight dictionary files and system
+program files makes this process very straightforward indeed. However,
+another annoying (and avoidable) glitch soon detracted from this friendly
+feature - the help associated with the MFS window didn't work. Pressing F1
+leads to a "HELP*2 is not an argument for MFS.SUB" error message. A quick
+analysis of the source code (yes, most of it is provided) soon identified
+the offending line (CASE ARG[1,5] = "HELP" - work it out for yourself), but
+it might be argued that a little more testing before release might have
+avoided this one! Certainly on the fourth prompt where the offending error
+("MGS.SUB cannot be executed...") is down to a simple spelling mistake, we
+have a right to expect better after shelling out our hard earned shekels.
+However, having said all this it must be emphasised that these are only
+installation errors, and the actual package itself works like a dream. Once
+it's installed you would never know it was there. The MFS quietly audits
+entries, amendments and deletions to programs, templates, popups etc..., it
+tracks new and amended dictionary items including symbolics, and picks up
+changes to the indexing via the dictionary item flags. The audited
+information is held in the PX file and can be examined at any time.
+Transmission of data is achieved by the command line utility PX
+(unfortunately there is no source code for this one). E.g.  PX TO A: creates
+transfer files, while PX FROM A: would import someone else's transfer files.
+The manual suggests that this is very much a two way process - changes from
+one site should be transmitted to a second site, then changes from the
+second site should be transmitted back to the first site. While some people
+doubtless work this way in practice, it would be very dangerous to attempt
+this sort of update using PX as there is NO contention logic in place.
+Instead of getting one unified application at the end you could easily end
+up with a worse mishmash than you started with whenever the same record has
+changed in different places! In practice it is better to make changes on
+only the master system for distribution to remote sites, but, caveat user!
+As PX currently stands (version 1.0) it must be installed on both master
+and remote sites, which leads greatly to temptation to use it as a
+two-way process. A nice feature would be for the PX TO process to create
+its own upload program when it makes a transfer. This would mean that PX
+would only ever have to be installed on the master site. Over to you Dave...
+(Added in latest version - Ed)
+Other PX command line options are to list current transactions, and to
+suspend and resume auditing. One minor gripe - where such lists are
+presented the report viewer is not used! It's just like being back in G2B
+(much loved then, but not missed now), and I hope that a generally
+excellent package isn't going to be judged too harshly on its failure to
+provide a consistent AREV interface.
+==== Conclusion. ====
+The package overall should prove invaluable to the serious developer
+responsible for maintaining distributed systems. The few blips found were
+solely in the set-up and interface processes, which show some signs of
+having been cobbled together quickly to get the in-house package onto the
+market. They are, however, fortunately minor, and I know that they are
+already being addressed for the next release.
+If all you care about are changes to programs (BP, TEMPLATES, POPUPS etc.)
+then you probably don't need PX; it is just as easy in practice to
+transfer the entire program volume. (Unless you're one of those
+unfortunates whose application was entirely developed in SYSPROG and
+REVBOOT, in which case PX is more of a necessity than a luxury!) The real
+strength of the package however, lies in its monitoring of changes to a
+dictionary, allowing changes to symbolics to be traced effortlessly, and
+also making the remote maintenance of indexing a delight rather than a
+chore.
+Given a certain Mr. McAuley's reliance on odd scraps of paper to track
+system enhancements (qui, moi? - Ed), suffice it to say that PX is likely to
+become a valuable addition to the Sprezzatura software library !
+==== Notes. ====
+PX has been tested in versions 1.16,2.03, 2.11 and 2.12 for DOS ONLY. Its
+transfer process relies heavily on the OS suite of commands, and it is not
+yet guaranteed for the OS/2 or UNIX versions of Advanced Revelation.
+PX is available for $139 from Harmacek Database Systems, 11 Grant Road,
+Winchester, MA 01890-1016. Telephone orders may be placed at (617) 721-1452,
+FAX via (617) 721-4656, CIS [73750-1044]. MasterCard, VISA, and
+corporate purchase orders are also accepted.
+(Volume 4, Issue 3, Pages 4-6)