If ISPVDLT is specified,
then each SAS variable is deleted from ISPF with the VDELETE user
exit before it is identified to ISPF with VDEFINE. This specification
prevents a SAS variable from being identified to ISPF more than once
in any SAS DATA step.
If NOISPVDLT is in effect,
then SAS variables are not deleted from ISPF before they are defined.
This specification can cause SAS variables to be defined to ISPF
more than once in a SAS DATA step.
To display the current
settings of your ISPF options, use PROC OPTIONS GROUP=ISPF.