https://library.netapp.com/ecmdocs/ECMP1196979/html/man1/na_snapvault.1.html

http://www.geekyfacts.com/index.php?option=com_content &view=article&id=64:snapvault

snapvault snap sched [ -f ] [ -x ] [ -o options ] [ volname [ snapname [ schedule ]]]

schedule is cnt[@day_list][@hour_list] or cnt[@hour_list][@day_list]

In the schedule, cnt tells SnapVault how many of the snapshots to keep for primaries and for non-SnapLock secondary volumes. The snapshots will be numbered newest to oldest from 0 to cnt-1. When creating a new snapshot, SnapVault will delete the oldest snapshots, increment by one the number on the remaining snapshots and then create a new number 0 snapshot. If a snapshot is missing from the sequence (e.g. sv.0, sv.1, and sv.3 exist but sv.2 does not), only snapshots that need to be renumbered to make room for the new sv.0 snapshot will be renumbered. In the example, sv.0 and sv.1 would be renamed to sv.1 and sv.2, but sv.3 would remain unchanged.

The cnt in the schedule is interpreted differently for SnapVault secondary SnapLock volumes. For SnapLock secondary volumes, snapshots are created with a name that includes an encoded date and time of when the snapshot is created. These snapshots are never renamed and they are never automatically deleted. These snapshots may be deleted using snap delete after the retention period of the snapshot has expired. If cnt is 0, no snapshots will be taken. If cnt is any non-zero value, snapshots will be taken and no snapshots will be automatically deleted.

If specified, the day_list specifies which days of the week the snapshot should be created. The day_list is a comma-separated list of the first three letters of the day: mon, tue, wed, thu, fri, sat, sun. The names are not case sensitive. Day ranges such as mon-fri can also be given. The default day_list is mon-sun, i.e. every day.

If specified, the hour_list specifies which hours of the day the snapshot should be created, on each scheduled day. The hour_list is a comma-separated list of the hours during the day, where hours are integers from 0 to 23. Hour ranges such as 8-17 are allowed. Also, step values are allowed in conjuction with ranges. For example, 0-23/2 means "every two hours". The default hour_list is 0, i.e. midnight on the morning of each scheduled day.