Epoch management parameters

The following table describes the epoch management parameters for configuring Vertica.

The following table describes the epoch management parameters for configuring Vertica.

Query the CONFIGURATION_PARAMETERS system table to determine what levels (node, session, user, database) are valid for a given parameter.
Determines how frequently (in seconds) Vertica checks the history retention status.

AdvanceAHMInterval cannot be set to a value that is less than the EpochMapInterval.

Default: 180 (seconds)

Blocks the advancement of the Ancient History Mark (AHM). When this parameter is enabled, the AHM epoch cannot be later than the epoch of your latest full backup. If you advance the AHM to purge and delete data, do not enable this parameter.

Default: 0

Determines the granularity of mapping between epochs and time available to historical queries. When a historical queries AT TIME T request is issued, Vertica maps it to an epoch within a granularity of EpochMapInterval seconds. It similarly affects the time reported for Last Good Epoch during Failure recovery. Note that it does not affect internal precision of epochs themselves.

Default: 180 (seconds)

Determines how long deleted data is saved (in seconds) as an historical reference. When the specified time since the deletion has passed, you can purge the data. Use the -1 setting if you prefer to use HistoryRetentionEpochs to determine which deleted data can be purged.

Default: 0 (Data saved when nodes are down.)

Specifies the number of historical epochs to save, and therefore, the amount of deleted data.

Unless you have a reason to limit the number of epochs, Vertica recommends that you specify the time over which deleted data is saved.

If you specify both History parameters, HistoryRetentionTime takes precedence. Setting both parameters to -1, preserves all historical data.

See Setting a purge policy.

Default: -1 (disabled)