### 21.1.2. Backup Tab

The Backup tab contains settings that specify the content of backup files, and the timesteps at which the files are written. The purpose of the backup file is to ensure that a solver run can be restarted. Backup files can be used to restart the simulation from the point where the error occurred, saving time and computational resources.

#### 21.1.2.1. List Box

This list box is used to select `Backup Results` objects for editing or deletion. `Backup Results` objects can be created or deleted with the icons that appear beside the list box.

The union of all requested backup file content, across all `Backup Results` objects applicable for a given iteration, is written as a single backup file for that iteration. If no backup file content is specified for a given iteration in any `Backup Results` object, then no backup file is written for that iteration.

#### 21.1.2.2. [Backup Results Name]

##### 21.1.2.2.1. Option

See Option.

##### 21.1.2.2.2. File Compression

See File Compression.

##### 21.1.2.2.3. Output Variables List

See Output Variables List.

##### 21.1.2.2.4. Output Equation Residuals Check Box

See Output Equation Residuals Check Box.

##### 21.1.2.2.5. Output Boundary Flows Check Box

See Output Boundary Flows Check Box.

##### 21.1.2.2.6. Output Variable Operators Check Box

See Output Variable Operators Check Box.

##### 21.1.2.2.7. Extra Output Variables List

When the Extra Output Variables List is selected, you can specify any variable that is not included in the results file by default. For more details, see Variables in ANSYS CFX in the CFX Reference Guide.

##### 21.1.2.2.8. Output Particle Boundary Vertex Fields Check Box

See Output Particle Boundary Vertex Fields Check Box.

##### 21.1.2.2.9. Include Tracks of One-way Coupled Particles Check Box

Select or clear the check box to include or exclude tracks of one-way coupled particles to be written to backup files. This option is available only for cases that involve one-way coupled particles. For details, see Particle Fluid Pair Coupling Options in the CFX-Solver Modeling Guide.

##### 21.1.2.2.10. Output Frequency: Option

See Output Frequency Options.

#### 21.1.2.3. Backup Data Retention

##### 21.1.2.3.1. Option

- `Delete Old Files`

  Deletes the previous backup file when a new backup file is created. This only corresponds to backups created with a specified output frequency. It does not apply to backup files created manually during a run. It also does not apply to backup files requested by a System Coupling system.

- `Keep All Files`

  Previous backup files are not deleted when a new backup file is created.

Release 18.2 - © ANSYS, Inc. All rights reserved.