HP Archive Backup System for OpenVMS Guide to Operations

Saving and Restoring Data
3.5 Saves and Restores
• Defining the date and time to be used as a basis for scheduling - all scheduling intervals are
based on both the date portion and time portion of the base date, and anniversaries of the
base date at intervals defined by the frequency attribute.
• Defining the basis for full versus incremental saves for complex frequencies such as dailyfull-weekly,
log_2 and log_3. The base date and appropriate anniversaries of the base date
define the date of the full saves.
Unless you want to change the scheduling or save type basis for the request, you would not
change the base date. As such, the base date will remain a date in the past. Compare this to the
start date, which specifies the next start date and time for the request. The start date is updated
whenever the request is run to reflect the next time it is scheduled, or NONE if it is not scheduled
again.
When a request is first created, and you specify only one of the dates, both dates are set (i.e. the
next start date is the base date). By default, neither a base date or start date are supplied so the
request is not scheduled for execution.
You can use the start date and skip time to request a one-time special, or non-scheduled, execution
of the request. For example, assume that the normal scheduled time for a request is 23:00, as
specified in the base date. However, you know that this is a particularly busy night and you want
to start this request for tonight only at 21:00 instead. You can do this by setting the start date to
21:00. However, when the request is rescheduled, it will be rescheduled to the next iteration of
the base date, or 23:00 the same day. You probably do not want this, so to avoid it you can set the
start date together with a skip time to avoid running the request twice. The skip time is an exclusion
time (expressed as a delta time) from the specified start date in which the request will not be
rescheduled: normally you can set this to one day to avoid running the request twice in the same
day. The following table shows some examples of base date, start date and skip time definitions
based on a daily frequency:
Table 3–2 Use of Base Date, Start Date and Skip Time
Base Date Start Date Skip Time Next Start
23-Aug 23:00 10-Sep 21:00 None 10-Sep 23:00
23-Aug 23:00 10-Sep 21:00 1-00:00:00 11-Sep 23:00
23-Aug-23:00 10-Sep-23:00 2-00:00:00 12-Sep 23:00
When you specify a skip time, ABS saves it in the database until the request is next rescheduled.
When the rescheduling takes place, the skip time is applied to the calculation, then cleared from
the database. If you set a skip time and do not see it in the request, then it has already been
applied to the next start date.
3.5.4 Before Date, Since Date and Date Archived (Restore Only)
When restoring files, you can choose a specific iteration of the files based on their archive date -
that is, the date that they were saved in the archive. If you know the exact date archived, use the
data archived attribute. If you know only an approximate date archived, use the before or since
attributes to specify a range of dates. So, for example, if you wish to restore a file as it existed in
the first week of January, you can specify a before date of the 8th January (at midnight), or a
since date of 1st January (at midnight). When determining appropriate before or since dates, you
should probably lookup the files in the catalog before requesting a restore, so that you can specify
before and since dates that uniquely identify a single iteration of the file to restore.
3-18 Saving and Restoring Data