FAMoS - an information service on the usage of data files in AliEn

The File Access Monitoring Service (FAMoS) leverages the information stored in the central AliEn file catalogue, which describes every file in a Unix-like directory structure, as well as metadata on file location and its replicas. In addition, it uses the access information provided by a set of API servers, used by all Grid clients to access the catalogue. The main functions of FAMoS are to sort the file accesses by logical groups, access time, user and storage element. The collected data identifies rarely used groups of files, as well as those with high popularity over different time periods. This information can be further used to optimize file distribution and replication factors, thus increasing the data processing efficiency. The paper describes the FAMoS structure and user interface and presents the results obtained in one year of service operation.