The Abaqus/Standard restart (.res) file and the Abaqus/Explicit state (.abq) file contain the information necessary to continue a previous analysis. In Abaqus/Explicit the package (.pac) file and the selected results (.sel) file are also used for restarting an analysis and must be saved upon completion of the first job. In addition, both products require the output database (.odb) file. Restart files can become very large for large models; when restart data are requested, they are written for every increment or interval by default. Thus, it is important to control the frequency at which restart data are written. Sometimes it is useful to allow data to be overwritten on the restart file during a step. This means that at the end of the analysis there is only one set of restart data for each step, corresponding to the state of the model at the end of each step. However, if the analysis is interrupted for some reason, such as a computer malfunction, the analysis can be continued from the point where restart data were last written.