The value of tmnxSysRollbackIndex indicates a specific rollback
checkpoint file to which a rollback action can be taken.
The value of the tmnxSysRollbackIndex corresponds to a rollback
checkpoint file with suffix .rb.index.
The maximum checkpoint file that can be specified is determined by
the rollback location as specified by tmnxSysRollbackLocation.
If the location is on a compact flash, then the maximum value of
tmnxSysRollbackIndex can be tmnxSysRollbackMaxLocalFiles minus 1.
If the location is a remote ftp location, then the maximum
value of tmnxSysRollbackIndex can be tmnxSysRollbackMaxRemoteFiles
minus 1.
This index is SET along with another action object, including
tmnxSysRollbackStart to initiate a rollback revert of a file
and tmnxSysRollbackFileDelete to delete a rollback file.
An SNMP GET request on this object should return the last SET value.