Saturday, February 1, 2020

Making a Backup Of your Model

It is an excellent idea to make a backup of your model from time to time.  This could be useful if you want to go back and open a previous model version.  In order to do that, you should periodically make a complete backup of your model and any additional files it might need.  You might not be able to run an old model if you don’t.  The complete archived model should include the same elements you would need to include if you sent the model to someone else to run.  Every model might not have all of these elements, but if they do, store them with that current version of the model.  The list is as follows:

  • Model
  • Custom libraries *
  • Custom Include files **
  • Pictures used for animation
  • External Data Files you are Importing from or Exporting to
* You don't need to backup the standard libraries which are installed with ExtendSim.  You only need to back up your custom libraries that are used in the model if you have any.  You might not have any but you will know it if you do.

** You don't need to backup the standard include files which are installed with ExtendSim.  You only need to back up your custom include files if you use any in custom block or the standard Equation blocks.

Consider one simple example of why you want to archive files along with the model itself.  Suppose we have an Excel workbook that is used to import data from the beginning of the run.  Let's say we have one tab for each of the input tables.  When we made a backup of the model, we did not back up anything other than the model.  Suppose we start working on the input data and made some changes to the model and the Excel workbook.  If we wanted to open the previous model and run it, we would have the archived model but we didn’t backup the spreadsheet so we would only have the updated spreadsheet.  The old model wouldn't understand what to do with this updated Excel file.  There would be a mismatch.  We would be able to open the model up in this case, but we couldn't run the model. 

The same concept applies to all the other files in the list above.  If we don't include them in the model backup, then when we go and open the backup model it may or may not work properly if there have been changes to the library files, include files, pictures, or data files.  These files can change over time as you enhance your model so it would be a great idea to keep a copy of these files with the model backup.
I use WinZip to make a complete backup of all the required files, but other tools could be used as well.  If you are working in a group of model developers, and everyone is working on the model, then something more advanced should be used which allows each user to "check in" changes on each individual file.  Source control tools can be used here.  The source control tools work well for keeping track of changes if the users document changes appropriately.

If you need to send your model to someone else to run, this same backup can be used.  Just don’t forget to include all necessary files. Your model might not contain all the files in this list, but if it does, then you will need to include it in the backup. 

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