What is a Mnesia checkpoint used for?

A checkpoint captures a consistent, point-in-time view of one or more tables while the system keeps running — it's the mechanism backups and certain replication operations use internally to get a stable snapshot without pausing the whole database.

{ok, Name, Nodes} = mnesia:activate_checkpoint(
    [{name, my_checkpoint}, {min, [person, session]}]),
mnesia:backup_checkpoint(Name, "/var/backups/partial.bak"),
mnesia:deactivate_checkpoint(Name).

mnesia:activate_checkpoint/1 retains the state of the specified tables as of that moment, even as new writes continue to happen afterward, so a subsequent backup_checkpoint/2 call reads a consistent snapshot rather than a moving target. Once the checkpoint is no longer needed, mnesia:deactivate_checkpoint/1 releases the extra bookkeeping Mnesia was doing to preserve that frozen view.

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