Recent versions of the sediment model write results to HDF5 and read those results with the sediment plotter. Sediment output files can get very large, and the HEC-RAS sediment transport model writes two additional files that can get very large (and affect run time) that may not be useful to users. HEC-RAS provides switches to turn these output files off.

The O file is the standard steady flow output file. Both the quasi-unsteady and unsteady sediment models write hydraulic results to the O file so users can view the standard hydraulic output with the standard hydraulic results tools (e.g. the profile plot, the cross section plot, the generalized output plot, the results tables).
Examples of the standard hydraulic results that read from the .O file (e.g. EuclidExample.O08). These plots will not work if the O file grows larger than 2GB it will not plot but users can still get sediment and hydraulic data from the Sediment Plotter. This feature can turn the .O file writes off if these files are too large.The 1D sediment model in HEC-RAS is a decadal scale model and is usually most effective when applied to multi-decadal calibrations and projections. So hydraulic output files can get large. If the O. file grows larger than 2GB, it will not plot and it has trouble writing to disk over 4GB. The sediment HDF5 file does not have these limitations (which is part of the reason HEC-RAS migrated to this file format). Therefore, HEC-RAS can plot the sediment results (and hydraulic output associated with the sediment results) if the fie gets large. 
Modelers can use the Output Increment to request less output. But this feature also allows users to turn the steady flow output off, saving disk space and run time, and get all of their results from the sediment plotter.
This option turns off the standard hydraulic output during a sediment simulation. Models that deselect this option will only write results to the sediment plotter.