The initial time step size is provided through TOUGH2 variable DELTEN or DLT(1), usually followed by automatic time stepping (see TOUGH2 variables MOP(16) and REDLT). The initial time step may be too big (i.e., is automatically reduced by TOUGH2) or too small (i.e., convergence is achieved within one Newton-Raphson iteration), depending on the parameter set supplied by iTOUGH2 during an inversion. This command allows iTOUGH2 to automatically adjust the initial time step size so that convergence is achieved within more than 1 but less than MOP(16) Newton-Raphson iterations. Automatic time step adjustment may improve the speed of an inversion, but may also make the inversion unstable if time discretization errors are significant.
>>> automatically ADJUST initial timestep DELTEN
>>> CONSECUTIVE | >>> REDUCTION