I've reading the UDB v8.2 Admin: Performance manual.

If one does backups, in a multi-partition database, with such a cycle:
Sun. - full offline
Mon. - incremental delta
Tues. - incremental delta
Wed. - incremental
Thurs. - incremental delta
Fri. - incremental delta
Sat. - incremental

and one wants to keep a month's worth of backups, what should the num_db_backups and rec_his_retentn values be?

According to the doc, if rec_his_retentn <> -1, then the recovery history file is pruned after every full database backup. Based on this, then do I assume that one should specify rec_his_retentn=-1, num_db_backups=around 35, and then one should have in place a PRUNE HISTORY?