Access policy

ARC usage credits

Access to the ARC service is supported by the University of Oxford through the Divisional Charging Model (top slicing), as well income from research grants and external use of the service.

Resources within ARC are based on a "credit" system and this is used 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 ARC Accounting page 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 ARC Accounting.  

Service level description

For more detailed 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' Quality of Service

Departments belonging to Divisions that do not contribute to the standard service (available through the Divisional Charging Model) are only entitled to use the Basic, free, Quality of Service. However, access via the Standard level Quality of Service can be gained via direct payment.

Standard Quality of Service

Departments belonging to Divisions that have agreed to contribute to service costs via top slicing (currently MPLS, SSD and Humanities) have paid for access to the standard service for their project users. Users from these Departments 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 to be conducted, and with details regarding how you have calculated the number of CPU hours required. This will not form part of a scientific peer review of you access request to the system and is only for reporting purpose, the ARC team will review the calculation in order to assess the correctness of the estimated time and also to advise on whether there are more efficient approached, this will help both with your research throughput and also to ensure the clusters are utilised efficiently. Please send this information to

Priority 'paid for' Quality of Service

This is a route for users who require and long-term usage of ARC facilities requiring quicker turn around times than standard mode on a job for job comparison (with respect to job size). Time can be purchased via a research grant or other source and this then provided users with access to the priority job submission queues on the ARC service. For users from Divisions that are part of the Divisional Charging Model Priority the cost of priority access credits is £0.01 per core hour and £0.02 per core hour for users accessing ARC under the Basic Quality of Service (as of 2020/21 Academic Year). 

Researchers who use ARC extensively and are writing grant proposals are strongly encouraged to incorporate ARC as 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