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memgraph/docs/dev/durability/snapshots.md
Dominik Gleich e67b06ab61 Move documentation 
Reviewers: buda, msantl, ipaljak

Reviewed By: ipaljak

Subscribers: teon.banek, pullbot

Differential Revision: https://phabricator.memgraph.io/D1476
2018-07-13 12:36:57 +02:00

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Snapshots

A "snapshot" is a record of the current database state stored in permanent storage. Note that the term "snapshot" is used also in the context of the transaction engine to denote a set of running transactions.

A snapshot is written to the file by Memgraph periodically if so configured. The snapshot creation process is done within a transaction created specifically for that purpose. The transaction is needed to ensure that the stored state is internally consistent.

The database state can be recovered from the snapshot during startup, if so configured. This recovery works in conjunction with write-ahead log recovery.

A single snapshot contains all the data needed to recover a database. In that sense snapshots are independent of each other and old snapshots can be deleted once the new ones are safely stored, if it is not necessary to revert the database to some older state.

The exact format of the snapshot file is defined inline in the snapshot creation code.