Retention period specifies how long the artifacts scan data will be kept by Xray; Prior to the retention policy, that became available on Xray 3.41.4, the retention period would be automatically set to forever.
Currently, If no retention period is set, 90 days is the default period for repositories and 15 days for builds.
Once the retention policy expires, all Xray data related to the repository/build will be deleted from the Xray database. More information regarding this topic can be found here .
In many cases, we can see repositories that are not getting fully indexed. This is usually caused due to an expired retention period for some artifacts inside the repository.