The value of tmnxSysRollbackSave indicates whether to save the existing
configuration in a rollback checkpoint file.
When SET to the value of 'doAction' the system will save the
configuration in a new rollback checkpoint file, with suffix '.rb'.
Previously saved rollback files with the same name will increment
the filename suffix by 1 upto a maximum of 9.
For example, file.rb is moved to file.rb.1. The higher the number,
the older the file is.
An SNMP GET request on this object should return 'notApplicable'.