This option is used to indicate that the step should be analyzed as a substructure generation step.
Product: ABAQUS/Standard
Type: History data
Level: This option is not supported in a model defined in terms of an assembly of part instances.
Set this parameter equal to the identifier to be assigned to this substructure in a substructure library. The identifier must be 
followed by a number that cannot exceed 9999.
Substructure identifiers must be unique within a library. If a substructure already exists in the library with this same identifier, the analysis will terminate with an error message unless the OVERWRITE parameter is specified.
Set GRAVITY LOAD=YES to calculate the substructure's gravity load vectors. The default is GRAVITY LOAD=NO.
Set this parameter equal to the name of the substructure library on which the substructure data will be written. See “Input syntax rules,” Section 1.2.1 of the ABAQUS Analysis User's Manual, for the syntax of such library names. The default library name is jobname.
Set MASS MATRIX=YES to calculate the substructure's reduced mass matrix. The default is MASS MATRIX=NO.
Include this parameter to overwrite an existing substructure with the same TYPE identifier in the library. The default is no overwrite.
Set this parameter equal to the frequency at which to evaluate frequency-dependent properties for viscoelasticity, springs, and dashpots during the substructure generation. If this parameter is omitted, ABAQUS/Standard will evaluate the stiffness associated with frequency-dependent springs and dashpots at zero frequency and will not consider the stiffness contributions from frequency-domain viscoelasticity in the *SUBSTRUCTURE GENERATE step.
Set RECOVERY MATRIX=NO to specify that output of element or nodal information will not be available within this substructure. The default is RECOVERY MATRIX=YES, indicating that recovery of internal variables will be possible for most analysis procedures. See “Using substructures,” Section 7.2.1 of the ABAQUS Analysis User's Manual, for further discussion.