The repository shall manage the number and location of copies of all digital objects.

This is necessary in order to assert that the repository is providing an authentic copy of a particular digital object.

Random retrieval tests; validation of object existence for each registered location; validation of a registered location for each object on storage systems; provenance and fixity checking infonnation; location register/log of digital objects compared to the expected number and location of copies of particular objects.

A repository can have different preservation policies for different classes of objects, depending on factors such as the producer, the information type, or its value. Repositories may require a different number of copies for each class, or manage versions needed to meet access requirements. There may be additional identification requirements if the data integrity mechanisms use alternative copies to replace failed copies. The location of each digital object must be described such that the object can be located precisely, without ambiguity. The location can be an absolute physical location or a logical location within a storage media

As part of the ingest workflow storing of digital items in the preservation storage, data is verified in the APTrust storing service after the object has been stored.

Regular 90-day fixity checking ensures consistent copies of all digital objects.

“Preserv checks fixity on all files in S3 and Wasabi storage every 90 days. We do not run fixity checks on files in Glacier or Glacier Deep archives.

apt_queue_fixity runs as a cron job in its own container, querying Registry every half hour for files that have not had a fixity check in 90 days. It typically gets a batch of 2,500 files at a time, then pushes all of the Generic File IDs into NSQ’s fixity_check topic.

From there, the apt_fixity worker picks them up, streaming each file through the sha256 checksum algorithm and creating a Premis event to record the result in Registry.”

Fixity process

Some of these workflow processes might just need updated documentaiton.