[MAS-tips] Tip: How to avoid the persistent settings compatibility problem

[Jim C. <jt...@di...>]

I may have mentioned this before in this forum, I can't remember for
sure, but it seems that a lot of mas users are not aware of this issue
and I think posting it here will be helpful, since following this tip
could help save people some time and irritation.

The issue is that sometimes a new version of the mas executable will not be
compatible with respect to the saved indicators and market analyzers (the
indicators_persist and generators_persist files).  However, preventative
action can be taken to avoid running into this problem.  It's described in
the FAQ entry copied below.  (The FAQ is at:
http://eiffel-mas.sourceforge.net/support/FAQ.html
.)

I recommend that everyone who creates their own indicators or market
analyzers get used to using this technique for creating and editing
indicators and analyzers, so that you can avoid compatibility issues in
the future.

Here is the FAQ entry:

I updated to a new version of MAS and when the server starts up it
prints the following error and exits: "Retrieval of indicator library
file indicators_persist failed. The file may be corrupted or you may
have an incompatible version." How can I use the old indicators I have
created with the new server?

This problem occurs when a new version of MAS incorporates a change to
the structure of the indicator code that is not compatible with the old
version. As a result, the old indicator file, indicators_persist, cannot
be loaded when the new version of the server starts up. Once this occurs,
the only way to use your old indicators is to keep using the old version
of the server. (This problem can also occur with market analyzers and
the generators_persist file.) However, there is a preventative method
that can be used to overcome the problem: Whenever you create a new
indicator, start the server in the background (-b option) and use the
command-line client program, macl, to talk to the server and "record"
the conversation with the command:

macl -r output_file <portnumber>

where output_file is the name of the file to which you wish to save
the recorded output and <portnumber> is the port number with which you
started the server. Keep this file in a safe place. It would probably
also be a good idea to keep it backed up.

Whenever you upgrade to a new version of MAS and get the above error
message, you can restore the indicators you have created by running the
following command on each of your recorded output files:

macl -i file <portnumber>

where file is the name of a file created earlier with the -r option
and <portnumber> is, again, the port number with which you started the
server. This solution works for both indicators and market analyzers.

Note for Windows users: Starting MAS the "normal" way, by clicking on the
MAS icon, will execute the necessary step described above of starting
the server in the background. However, you will still need to run the
'macl -r ...' and 'macl -i ...' commands described above from the Windows
command line. Those who do not know how to do this may want to wait for
a future release in which this procedure is handled automatically.