Virtual Active File

The virtual active file enables you to work with large data files without requiring equally large (or larger) amounts of temporary disk space. For most analysis and charting procedures, the original data source is reread each time you run a different procedure. Procedures that modify the data require a certain amount of temporary disk space to keep track of the changes, and some actions always require enough disk space for at least one entire copy of the data file.

Actions that don't require any temporary disk space include:

  • Reading IBM® SPSS® Statistics data files
  • Merging two or more IBM SPSS Statistics data files
  • Reading database tables with the Database Wizard
  • Merging IBM SPSS Statistics data files with database tables
  • Running procedures that read data (for example, Frequencies, Crosstabs, Explore)

Actions that create one or more columns of data in temporary disk space include:

  • Computing new variables
  • Recoding existing variables
  • Running procedures that create or modify variables (for example, saving predicted values in Linear Regression)

Actions that create an entire copy of the data file in temporary disk space include:

  • Reading Excel files
  • Running procedures that sort data (for example, Sort Cases, Split File)
  • Reading data with GET TRANSLATE or DATA LIST commands
  • Using the Cache Data facility or the CACHE command
  • Launching other applications from IBM SPSS Statistics that read the data file (for example, AnswerTree, DecisionTime)

Note: The GET DATA command provides functionality comparable to DATA LIST without creating an entire copy of the data file in temporary disk space. The SPLIT FILE command in command syntax does not sort the data file and therefore does not create a copy of the data file. This command, however, requires sorted data for proper operation, and the dialog box interface for this procedure will automatically sort the data file, resulting in a complete copy of the data file. (Command syntax is not available with the Student Version.)

Actions that create an entire copy of the data file by default:

  • Reading databases with the Database Wizard
  • Reading text files with the Text Wizard

The Text Wizard provides an optional setting to automatically cache the data. By default, this option is selected. You can turn it off by deselecting Cache data locally. For the Database Wizard, you can paste the generated command syntax and delete the CACHE command.