The best approach to running DL_POLY_2 is to define from the outset precisely the simulation you wish to perform and create the input files specific to this requirement. The program will then perform the requested simulation, but may terminate prematurely through error, inadequate time allocation or computer failure. Errors in input data are your responsibility, but DL_POLY_2 will usually give diagnostic messages to help you sort out the trouble. Running out of job time is common and provided you have correctly specified the job time variables (using the close time and job time directives - see section 4.1.1) in the CONTROL file, DL_POLY_2 will stop in a controlled manner, allowing you to restart the job as if it had not been interrupted.
To restart a simulation after normal termination you will again require the CONTROL file, the FIELD (and TABLE) file, and a CONFIG file, which is the exact copy of the REVCON file created by the previous job. You will also require a new file: REVOLD (section 4.1.4), which is an exact copy of the previous REVIVE file. If you attempt to restart DL_POLY_2 without this additional file available, the job will fail. Note that DL_POLY_2 will append new data to the existing STATIS and HISTORY files if the run is restarted, other output files will be overwritten.
In the event of machine failure, you should be able to restart the job in the same way from the surviving REVCON and REVIVE files, which are dumped at intervals to meet just such an emergency. In this case check carefully that the input files are intact and use the HISTORY and STATIS files with caution - there may be duplicated or missing records. The reprieve processing capabilities of DL_POLY_2 are not foolproof - the job may crash while these files are being written for example, but they can help a great deal. You are advised to keep backup copies of these files, noting the times they were written, to help you avoid going right back to the start of a simulation.
You can also extend a simulation beyond its initial allocation of timesteps, provided you still have the REVCON and REVIVE files. These should be copied to the CONFIG and REVOLD files respectively and the directive timesteps adjusted in the CONTROL file to the new total number of steps required for the simulation. For example if you wish to extend a 10000 step simulation by a further 5000 steps use the directive timesteps 15000 in the CONTROL file and include the restart directive. You can use the restart scale directive if you want to reset the temperature at the restart, but note that this also resets all internal accumulators (timestep included) to zero.