If present, the VBDUMP card must occur first in the CASVB input. It is not required for variational calculations.
Note that in the majority of cases (e.g., if a CASVB run occurs immediately after MULTI, or for variational calculations), explicit specification of dump records with vbdump is not required.
Wavefunction definitions may be restored here using VBDUMP cards
(see also Section 20.8.6).
The default record name (vbdump) is 4299.2. If a VBDUMP card is not present and record 4299.2 does not exist, then
CASVB will attempt to generate the wavefunction information
automatically based on the latest MCSCF calculation (however, STATE
and WEIGHT information will not be restored in such a case).