Keeping and Opening Recovery Files
The COMSOL Multiphysics software can save and keep recovery files each time you start a solver. This setting is initially active by default. If the server has lost contact with the client, a recovery file is also saved or kept.
If any recovery files exist, the Recovery Files window is open when you start the COMSOL Desktop. You can also open the Recovery Files window from the Windows menu.
The update of the recovery file occurs at the following events:
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After completing the solution for each time step specified as the output times in the Times field for a time-dependent simulation.
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After completing each parameter step in a parametric simulation.
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After completing each successful Newton iteration for a nonlinear stationary simulation.
The recovery files are COMSOL MPH-files that represent the state at the time that they were saved. They make it possible to recover from a solver error, which can be especially useful for long time-dependent or parametric runs.
The size of the recovery file is about the same as the MPH-file for the corresponding model.
If you want to reduce the amount of solution data stored in a COMSOL model, see the information here: https://www.comsol.com/support/learning-center/article/Reducing-the-Amount-of-Solution-Data-Stored-in-a-Model-67151.
Do not delete files manually in the folders for recovery files and temporary files. Doing so can affect the model in an open COMSOL Desktop session. These files are deleted automatically when exiting the COMSOL Desktop session.
The recovery file for the previous model are kept until you create or opening a new model. It is also deleted when exit the COMSOL Desktop.
You can control the use of recovery files using the buttons at the top of the Recovery Files window:
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Click the Open button () to open a selected recovery file. Opening recovery files this way ensures that the recovery file can be deleted without compromising the open model. It does not remove the recovery file when the open model is saved, though.
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Click the Save and Open () button saves the recovery file to a Model MPH-file and open it. It also removes the recovery file.
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Click the Save As button () to save the recovery file to a Model MPH-file and remove the recovery file.
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Click the Delete button () or press Delete to remove the selected recovery files.
The COMSOL Multiphysics software keeps track of the computed time steps or parameter steps in the recovery file, so right-click the Study node and select Continue () to continue the computation from the point where it was stored in the recovery file. If you are solving a stationary nonparametric problem, the last converged Newton iteration is stored in the recovery file; selecting Continue causes the software to resume solving from this stored state.
You can make changes to these default settings in The Preferences Window on the Files > Recovery page.
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The Check for recovery files at launch checkbox is selected by default so that the Recovery Files window opens at launch when there are any recovery files.
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The Keep recovery files when the application terminates unexpectedly checkbox is selected by default to keep recovery files on disk during the solution process for time-dependent, parametric, and nonlinear solvers. Because the folder for recovery files is also used for unloading data, the amount of disk space that you save is limited.
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In the Folder for recovery files field, you can specify a different folder from the default to, for example, use a folder on the server where there is more disk space for keeping large recovery files. Click Browse () to browse to a recovery file folder.
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From the Recovery saving list, choose On every iteration (the default) or Saving ratio. If you chose Saving ratio, also enter a ratio in the Recovery saving ratio field (default: 0.1; that is, saving every 10:th iteration). The recovery saving ratio is a number between 0 and 1.
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If desired, select the Save every checkbox to save a solution with a time interval in seconds that you enter in the associated text field (default: 1800 s; that is, once every half hour). This time interval is the longest time that is allowed to pass before the recovery file is saved while computing.
Also, on the main Files page, in the Folder for temporary files field, you can specify a different folder than the default to, for example, use a folder where there is more disk space for keeping large temporary files. Click Browse () to browse to a folder for temporary files. If you run the COMSOL Multiphysics software in a client-server configuration, you can specify a Folder for temporary files on client and a Folder for temporary files on server.
There are also similar settings for saving recovery files in the settings for the Advanced solver node. By default, they use the settings from the Preferences window.
The folder for recovery files is used both for storing recovery files that can be used to recover the model if the COMSOL Multiphysics simulation ends unexpectedly and for unloading data from memory. The folder for recovery files is therefore still filled with data even if you have cleared the Keep recovery files when the application terminates unexpectedly checkbox.
Studies and Solvers