Thanks for reaching out. I am running an explicit dyniamic time history analysis.
 In the Control_Implicit_auto, I have set IAUTO = 0 to ensure a constant time step. I have also specified DTMIN = 1.2e-7sec and  added a table to control DTMAX. In Control_implicit_general, IMFLAG = 0 for explicit analysis. Perhaps, it is not clear to me how Ls Dyna works. For the purpose of my research, I need to have constant time step for the results to be accurate. If Ls Dyna skips a several time steps, the results may be incorrect. Thus, I would like to control the maximum timestep.