Access policy

ARC usage credits

Access to the ARC service is supported by the University of Oxford through departmental subscriptions and income from research grants.

ARC uses a "credit" system to keep track of resource usage on the ARC clusters, with one credit translating to running for 1 second of wall clock time on a single CPU core.  Please read our Accounting System page for more details on how credit usage is calculated for jobs.

ARC usage credits are "free" for researchers in the University of Oxford, in the sense that researchers do not have to pay directly to gain access to the ARC service.  However purchasing credits (e.g. from research grants) gives access to an elevated level of service, the main benefit of which is a more rapid turnaround of jobs.If you need to purchase credits, please see the page Requesting usage credits for more information.

Initial allocation of credits

All new projects are set up with an initial 25,000 CPU hours (90,000,000 credits).  This is enough to get your software/applications set up and also do some initial testing, benchmarking or even experimentation.  Beyond that, you need to request extra credits, process which is explained in Requesting usage credits.  

Service level description

For more detailled information on our service and quality of service (job resource and priority) levels, see the document here: Service Level Agreements & Quality of Service.

Basic 'Free' Service

Departments that do not contribute to the standard service are only entitled to use the Basic, free, service. Access to the standard service and priority service is via direct payment.

Standard Service

Departments that have paid for access to the standard service for their users are entitled to unlimited use of the standard service. If you are not able to fund time via a Research Grant then please select this option. There is no limit on usage and no charge to the users.

To request further credits all we require is a brief proposal outlining the research with the details of the number of CPU hours required. Please send this to

Priority 'paid for' Service

This is the preferred route for users who require sustained and long-term usage of ARC facilities. Purchasing time via a research grants gives users access to the priority job submission queues

Researchers who use ARC extensively and are writing grant proposals are strongly encouraged to add a directly allocated cost item for this purpose.


Service level implementation

The following table provides a summary of the service levels:

Funding Source Job Scheduler Priority Max Job Run Time (hours) Access to Advice/Support CPU Hour Allocation
Paid for Service via Research Grants HIgh 120  Priority As purchased
Standard Service Normal 120 When Available Fairshare usage
Basic Service Normal 24 When Available Fairshare usage