Dynamic configuration of the CMS data acquisition cluster

The CMS Data Acquisition cluster, which runsaround 10000 applications, is configureddynamically at runtime. XML configurationdocuments determine what applications are executed on each node and over what networks these applications communicate. Through this mechanism the DAQ System may be adapted to the required performance, partitioned in order to perform (test-) runsin parallel, or re-structured in case of hardware faults. This paper presents the configurationprocedure and the CMS DAQ Configuratortool, which is used to generate comprehensive configurationsof the CMS DAQ system based on a high-level description given by the user. Using a database of configurationtemplates and a database containing a detailed model of hardware modules, data and control links, nodes and the network topology, the tool automatically determines which applications are needed, on which nodes they should run, and over which networks the event traffic will flow. The tool computes application parameters and generates the XML configurationdocuments and the configurationof the run-control system. The performance of the configurationprocedure and the tool as well as operational experience during CMS commissioning and the first LHC runsare discussed.