Mechanical APDL Basic Analysis Guide

5.8.1.1.1. Multiframe Restart Limitations

Multiframe restart has the following limitations for a nonlinear static analysis, a nonlinear full transient
analysis, or a linear full transient analysis:

• Material properties or elements cannot be changed during a restart.


• The factorized matrix cannot be reused (KUSE). A new stiffness matrix and the related .LN22 file is
  regenerated.


• The .Rnnn file does not save the EKILL and EALIVE commands. If EKILL or EALIVE commands are
  required in the restarted session, they must be issued again.


• The .RDB file saves only the database information available at the first substep of the first load step.
  If other information is input after the first load step and that information is needed for the restart, it
  must be input again in the restart session.This situation often occurs when parameters are used
  (APDL); issue the PARSAV command to save the parameters during the initial run, and PARRES restore
  them in the restart. The situation also occurs when changing element REAL constants values; in this
  case, reissue the R command during the restart session.


• A restart cannot occur at the equation solver level (for example, the PCG iteration level). The job can
  only be restarted at a substep level (either transient or Newton-Raphson loop).


• An analysis cannot be restarted with a load step number larger than 9999.


• Multiframe restart does not support the arc-length method (ARCLEN command).


• All loading and boundary conditions are stored in the Jobname.LDHI file. Upon restart, removing
  or deleting solid modeling loading and boundary conditions does not remove these conditions from
  the finite element model. Loading and boundary conditions must be removed directly from nodes
  and elements.


• To terminate a nonlinear analysis "cleanly" on a multitasking operating system, create an abort file
  named Jobname.ABT in the working directory (or on some case-sensitive systems,jobname.abt).
  This file should contain the word nonlinear in the first column of the first line. If the program locates
  this file at the start of an equilibrium iteration, the analysis stops and can be restarted at a later time.


• The database file (Jobname.DB) saved by the user (SAVE command) is not used by the restart. The
  Jobname.RDB file, which is a database file saved automatically by the program at the start of the
  first substep of the first load step, is used by the restart.


• Nested *DO loops are not supported for restarts.


• The first time step of a restarted transient solution using the HHT algorithm (TRNOPT) uses the
  Newmark algorithm. Subsequent time steps use the HHT algorithm.


• For the case of distributed memory parallel processing, you must use Distributed ANSYS prior to and
  during the restart, and the core count must be consistent. See Restarts in Distributed ANSYS in the
  Parallel Processing Guide for a more detailed description of how to perform restarts in Distributed
  ANSYS.

5.8.1.2. Multiframe Restart Procedure

Use the following procedure to restart an analysis:

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Restarting an Analysis