# About SUM baselines

Baselines are directories that contain update components SUM can apply to local and remote nodes. Some baselines include:

- SPP

- Custom SPP downloads

- Maintenance Supplement Bundle

- Custom baselines/ISOs created by SUM

When you add a baseline, SUM searches for the following files:

- `bpxxxx.xml` file: Lists the name, version, history, and components in the baseline. SUM treats any components in the directory that are not listed in the `bpxxxx.xml` file as an Additional Package, not as the main baseline. The SPP, Maintenance Supplement Bundle, and custom baselines include the `bpxxxx.xml` file.

- `..\manifest` directory: This directory contains details about all components contained in the baseline. Included in the manifest directory are:

  - `meta.xml`: Contains most of the component xml file data.

  - `primary.xml`: Contains details about RPMs in the baseline.

  - `system.xml`: Contains mapping information between ROM family and system model.

  - `revision_history.xml`: Contains history information for the component.

- `\db\BaselineDB.pdb`: This is a prepopulated database that SUM uses if there is no other database from other baselines. This file contains all details for the components when the baseline was generated. SPPs and custom baselines include prepopulated databases.