get_last_good_epoch() not advancing so can't drop old projections

Determines how long deleted data is saved (in seconds) as a historical reference. The default is 0, which means that Vertica saves historical data only when nodes are down. Once the specified time has passed since the delete, the data is eligible to be purged. Use the -1 setting if you prefer to use <CODE>HistoryRetentionEpochs for determining which deleted data can be purged.

Note: The default setting of 0 effectively prevents the use of the Administration Tools 'Roll Back Database to Last Good Epoch' option because the AHM remains close to the current epoch and a rollback is not permitted to an epoch prior to the AHM.

Tip: If you rely on the Roll Back option to remove recently loaded data, consider setting a day-wide window for removing loaded data; for example:

<CODE>SELECT SET_CONFIG_PARAMETER ('HistoryRetentionTime', '86400');