LSDYNA UMAT- history variable choice

Hi,

I'm presently working on implementing anisotropic yield criteria in LSDYNA as UMAT.

I understand from the LSDYNA documents that effective plastic strain is a default history variable.  So when we code, can we omit the update of effective plastic strain as a history variable? If so, where is it stored and how is it retrieved during post-processing ?

In addition to the above, What should we enter in the 'NHV' - number of history variables in the input deck? Should we include effective plastic strain or is it suficient to worry only about the additional history variables we enter (assuming we need not update eff. plastic strain as a separate histroy variable )

 I will be thankful if someone could throw some light on this.