Specifications

2
Software Architecture
29
Shelf FRU information redundancy
DuringnormalshelfoperationwithredundantShelfManagers,therearealwaysatleastthree
persistentcopiesoftheshelfFRUinformation.TheshelfFRUinformationisinitiallystoredina
singleshelfFRUdeviceinanATCA‐6000shelf,andintwoshelfFRUdevicesinanATCA‐6006,
ATCA‐6014,orATCA‐6016shelf.Inaddition,boththeactiveandstandbyShelfManagerskeep
apersiste ntcacheoftheshelfFRUinformation.OneofthefirststepstakenbytheactiveShelf
Managerduringinitializationislocating,validating,andcrea tingorupdatingthesepersistent
cachesoftheshelfFRUinformation.
TheactiveShelfManagervalidatesthechecksumofeachshelfFRUinformationfileandalso
comparesthecontentsofthefilestoresolveanyconflicts.Ifaconflictexists,theShelf
ManagergivesprioritytotheshelfFRUdevicecontentsoverthecopiescachedbytheShelf
Manager.OncetheShelfManageridentifiesgoodcontent,itcopiesoverthecontentofthe
otherlocationsiftheircontentsdiffer.
TheShelfManagerusesthesebasicrulestoselectgoodcontent:
•IfashelfFRUdevice’schecksumisvalid(anditscontentdoesnotconflictwithanother
shelfFRUdeviceontheATCA‐6006shelf),theShelfManagerselectstheshelfFRUdevice
content.
•IfnoshelfFRUdevicehasavalidchecksumbutthecopiescachedbyboththeactiveand
standbyShelfManagerhavevalidchecksumsandmatchingcontent,theShelfManager
selectstheactiveShelfManager’scachedcontent.
•IftwoshelfFRUdeviceshaveconflictingcontent,theShelfManagercomparestheir
contenttotheShelfManager‐cachedcopiesandselectstheshelfFRUdevicecontentthat
matchesmorecachedcopies.
Note:ThisruleappliestotheATCA‐6006shelfonly.AlthoughtheATCA‐6014and
ATCA‐6016shelveseachhavetwoshelfFRUdevices,only oneisread—thedevice
accessibletotheactiveRCM.Thecontentsofthetwodevicesarenotcompared.
•IfvalidshelfFRUinformationcannotbelocatedoraconflictcannotbere solved,theShelf
Managergenerate sashelfFRUInvalidalarmtorequestoperatorassistanceinupdating
theshelf
FRUinformation.