# TLA+ Preferences

There are three preferences that can be set on this page.

### Continue Previous Session on Restart

This option allows you to choose whether, when you close the Toolbox, it resumes from where you were (the default) or opens the Welcome View.

### Minimum spec storage displayed

The Toolbox keeps all the information about a specification name `Spec`, other than its actual files, in a folder named `Spec.toolbox`. When that folder becomes sufficiently large, its size is shown near the bottom right-hand corner of the Toolbox window. This parameter specifies how large (in kilobytes) sufficiently large is. The default is 50 megabytes.

When the `.toolbox` folder becomes very large, it is probably because it contains one or more checkpoints created by TLC. The checkpoint is deleted if TLC completes successfully, but is saved if TLC is stopped or finds an error. A TLC execution that takes several days can create a checkpoint with more than a gigabyte of data. When a spec uses a lot of space, you should view the TLC models you have created for it to see if any have large checkpoints. See Checkpoint Recovery to learn how you can find out how large a checkpoint is and how you can delete a checkpoint.

### Library Folders

This specifies a list of library folders that are for modules that may be used in more than one specification. When a specification imports a module (with an `EXTENDS` or `INSTANCE` statement), the parser searches for that module first in the root module's folder, then in the sequence of specified library folders (in the order they appear in the list), then among the standard modules. The list of library folders specified here can be overridden for a particular spec with a different list in the spec's Spec Explorer entry.

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