A Digital Archive should follow the OAIS reference model, which technical part can be summarized as follows.

Each object (information asset) should be stored in a self-sufficient "bag", allowing disaster recovery and long-term survival of its content, authenticity and description. The reference supports a packaging in the form of AIP, Archival Information Package.

It must have redundant copies.
It must be regularly checked.  
It must be supported by a preservation plan.

It must be sustained by an organizational policy.

The OAIS model also defines a workflow from the initial submitted information into the Digital Archive. The source information might come from active Information Systems (databases, institutional repositories, administrative systems, etc), feed the archive with Submission Information Package that are converted into the AIP.

The OAIS Archive can then be transformed into Dissemination Information Package for end-users.