The usage of rowNum equal to -1 or other negative value is wrong and not supported (at list for local jqGrid data). If you look at the documentation you can see that the sentance about -1 value is removed. You can use any large value instead (1000, 10000), but it is strictly recomended to use small values of rowNum which follows to data pagination. It is much more effective and comfortable for the user. No display can show 1000 rows at once. Scrolling of data inside web browser is less effective as jqGrid pagination. Moreover no real person are able to read and analyse so many information items. The usage of toolbar searching, advance searching and other searching possibilities of jqGrid could provide together with the local pagination the best user expirience.

Best regards
Oleg