Revision management

By default, Yoda stores revisions of data objects up to 2 GB, so that users can restore earlier versions of these data objects if needed. The revision store is located at /tempZone/yoda/revisions (where tempZone is the zone name).

Revision strategies

Yoda uses a revision strategy that defines which revisions need to be kept. Revisions that don’t need to be kept as per this policy are removed by the daily revision cleanup job. A revision strategy consists of a series of successive time buckets, where the first bucket starts in the present. For example, in strategy A (see table below), the first bucket refers to all revisions created in the last six hours, the second bucket refers to all revisions created in the twelve hours before that, and so forth. Yoda uses strategy B by default.

Yoda supports four built-in strategies:

• A
• B (default)
• Simple
• Fourweeks

If a data object has any revisions in a defined bucket, the cleanup job removes revisions that do not belong to any bucket. If a data object has no revisions in defined buckets, the cleanup job decides what happens based on the always_keep_one parameter:

• True – keep the single most recent revision outside the span. This ensures that at least one revision of data object.
  (strategies A, B, Simple)
• False – remove every revision that is older than the span
  (strategy Fourweeks)

Strategy A:

time bucket	number of revisions
6 hours	1
12 hours	1
18 hours	1
1 day	1
2 days	1
3 days	1
4 days	1
5 days	1
6 days	1
1 week	1
2 weeks	1
3 weeks	1
4 weeks	1
8 weeks	1
12 weeks	1
16 weeks	1

Strategy B:

time bucket	number of revisions
12 hours	2
1 day	2
3 days	2
5 days	2
1 week	2
3 weeks	2
8 weeks	2
16 weeks	2

Strategy Simple:

time bucket	number of revisions
16 weeks	16

Strategy Fourweeks:

time bucket	number of revisions
1 day	2
6 days	2
21 days	2

always_keep_one for Fourweeks is False, meaning anything older than 28 days (the total span of the three buckets) is removed completely rather than retaining a final safety copy.