Oab not updating on cas server
In previous versions, Microsoft Exchange File Distribution Service on the CAS role was pulling the OAB files, and passes it to the clients on request.Bu in Exchange 2013, Exchange CAS 2013 proxies all OAB download requests to the appropriate Exchange 2013 Mailbox server.The database will be mounted on another server according to the activation preference.So if CAS server receives another request for OAB download it then queries to Active Manager for the current active mailbox server to process the request.Whereas in Exchange Server 2013 “OABGenerator Assistant” (mailbox agent running under the Microsoft Exchange Mailbox Assistant service) generated the OAB. In Exchange Server 2013, the OAB files are stored in the Organization Mailbox first and later the contents are copied to folder.Good part is, “OABGenerator Assistant” is a throttled process and it pauses and resumes according to the load of a server to give a maximum server performance. As it mentioned, it is no more accessible to CAS server via shared like in previous versions, hence the CAS server proxies such requests to the mailbox server where the database of Organization mailbox is active.You don't need to specify a value with this switch.
Microsoft Exchange Team has introduced a major change in architecture of OAB in Exchange Server 2013, mainly targeting to avoid the single point of failure of OAB generation process.
The database homing the System mailbox should be active and mounted.
Clients will contact the mailbox server on which the OAB files are and downloads directly using Auto Discover.
For information about the parameter sets in the Syntax section below, see Exchange cmdlet syntax (https://technet.microsoft.com/library/bb123552.aspx).
The Update-File Distribution Service cmdlet forces the Microsoft Exchange File Distribution service to reload its configuration and poll for new data associated with OAB, Group Metrics, and Unified Messaging configuration.