snmpconf Persistence definition

Hi all, 

Just wonder if there is any definition of persistence related to MIBs in
any RFC?

"3.7 Persistent Configuration" in draft-ietf-snmpconf-bcp-10.txt is a
good starting point at least to figure out whether an object needs or
not a persistent reference by DESCRIPTION or storageType object.

The Q came to me as 
"Webstern dictionary definition", sysDescr is persistent (persist,
ramain the same), 
but  not in the MIB scope, isn't it?

MIB persistence (also from 3.7 cases description) I guess is more like
if a value was changed/added and must be keep, then the object persist,
but haven't find any good reference/glossary term about persistent in
RFCs 

Thanks

Eduardo