Open Access Repositories can be either linked to an institution or department or linked to a research field or subject, i.e. Institutional or Subject Repositories.
When using the OpenAIRE deposit service you will be guided through the steps of deposition and also if possible guided to a relevant repository. OpenAIRE uses data from the Directory of Open Access Repositories, OpenDOAR.
Publisher's policies relating to self-archiving can be checked at the SHERPA/RoMEO website.
There are several resources to find repositories:
!!! OpenDOAR and thus OpenAIRE may not be comprehensive. Go to the OpenAIRE helpdesk if you are having trouble finding a suitable repository.
You can also use ZENODO, the former OpenAIRE 'Orphan Repository'. ZENODO is hosted by CERN and accepts both publications and datasets.
Some journal publishers also have agreements with OpenAIRE and allow harvesting from their archives. Check with your publishers to find out if they participate.