Transaction Logs and Snapshots

Each partition on a node has a set of transaction logs that contain database updates made by DDL and DML commands. A snapshot is a database backup that contains only the in-memory rowstore data (of committed transactions). A snapshot is triggered each time the size of transaction logs reaches a predefined threshold. Snapshots can also be triggered manually for individual databases.

Transaction logs that are committed to snapshots are truncated to save disk space. In addition, old snapshots can be periodically deleted by configuring engine variables. At any given point, only transaction logs that are currently used by snapshots are stored on the disk.

Note that transaction logs are not stored in a human-readable format, unlike query log that is a text file.

The following sections provide general information about transaction logs and snapshots and further explain how to configure and manage the disk space used by them.