Adaptive Data Retention
Dynatrace periodically deletes transaction storage, Session Replay storage, and Log monitoring storage data that is older than the configured retention time. Adaptive Data Retention is a functionality according to which Dynatrace periodically increases or decreases the retention time of this data if the tenant environment storage quota is exceeded.
Each data type stored on a disk has a default retention time, which specifies how long that data type can be stored on disk. See Data retention periods for more details.
The maximum amount of a given data type that can be stored on disk is determined as follows:
The configured retention time defines how long data of a certain type should be stored on the disk. Older data is periodically deleted.
The adapted retention time is the configured retention time reduced by a factor calculated when the tenant data exceeds its quota. If this condition doesn't apply, the adapted retention time is equal to the configured retention time.
For example, suppose all of the following statements are true:
The configured retention time of Session Replay storage data is 10 days
The environment has exceeded its session storage data quota
The factor for calculating adapted retention time is 10%
In this case, the adapted retention time would be 9 days for session storage data:
Real retention time = 10 days × ((100 − 10) ÷ 100) = 10 × 0.9 = 9 days
This would result in all Session Replay storage data older than 9 days being deleted immediately, even though the configured retention time is 10 days.
How retention time is adapted
Retention time is decreased if the environment uses more disk space than its quota allows. This condition is continuously evaluated. If it's violated, retention time is decreased and deletion of data older than the adapted retention time begins.
After data is deleted according to the adapted retention time:
If enough data was deleted and neither of the conditions is currently violated, then the retention time is increased again.
If at least one of the conditions is still violated, the retention time is further decreased, and more data is deleted.
What to do if the retention time is adapted
Adaptation of data retention time can be caused by an undersized disk or an inappropriate quota.
To prevent unwanted adaptation of retention time for data:
Increase your quota
Increase your disk size
Adaptive Data Retention is impacted by several factors. Under certain rare circumstances, the adaptation of retention time can lead to excessive data deletion for an environment. As a result, the amount of processed data that is retained and the amount of available storage, which is limited by disk space or quota, are not aligned.
To mitigate this issue:
Increase the available disk space or quota.
Decrease the retention time for that environment so that adaptation has less impact.
How does a decrease in retention time affect retention time adaptation?
Because retention time adaptation is a percentage of your data retention time, a longer data retention time proportionally causes more data—and therefore more hours—to be deleted.
How does adding a new environment affect the existing environments on a cluster running on full disks?
As the new environment takes up disk space, the existing environments' retention times are gradually decreased. After some time, all of the cluster's environments have the same percentage change of their configured data retention times.
Why is the current retention time lower than the configured retention time even though there seems to be enough free disk space?
Some deviation is expected. When the deviation is too extreme, the required disk space for the configured retention time usually diverges heavily from the available disk space. Try setting the retention times to a more realistic value better suiting the currently available disk space.
Why was the data retention time reduced more than what CMC shows as the value for the reduction?
The Adaptive Data Retention reduction displayed in Cluster Management Console is only a snapshot of the current situation. After the data is removed from the disk, the reduction is decreased continuously, resulting in this behavior.