The Trim operation allows you to trim the run to a smaller size, by throwing out all the data outside of the current analysis range. You have the option of creating a "New run", which is a trimmed version of the current run, or you can "Overwrite" the current run directly. If you are creating a new run, you will be asked to enter the run file name for this new run. If you enter the name of an existing run file, or if you are overwriting the current run, you will be asked for confirmation before the run is overwritten.
When the run is trimmed, frames in the frame file outside of the current analysis range are thrown out, and all waveform data files are shrunk so as to include only samples in that range. The trimming is performed in temporary files, so you will need enough free disk space to hold the trimmed run, even if you are overwriting an existing run. This operation does not preserve links; even if waveform data files are linked together in the current run, separate data files are generated for each waveform in the trimmed run.
Note that neither the analysis parameters, nor the waveform parameters, are changed by this operation. If you create a new run, none of the parameter files are copied. If you trim your current run, the time-related parameters will no longer be properly set, and will eventually have to be re-entered. (These include the analysis range and the spike and cycle activity bursts for all waveforms.)