Example: The values in the above screenshot mean OAB is generated once every day.The Exchange Server 2013 CAS role proxies the OAB download request to an appropriate Mailbox role server.For a non-DAG environment, use following command to identify the OAB Generation servers: Get-Mailbox -Arbitration | where | ft name,servername For a DAG environment, identifying OAB generation server(s) is a two-step process.Step1: Identify the mailbox database hosting organization mailbox with OAB Gen capability.It can proxy the request in round robin fashion if it finds more than one organization mailbox active in same AD site.Prior to CU5, this will result in frequent full OAB downloads and is therefore, not recommended.You might see a “Schedule” defined when viewing properties of Exchange 2013 OAB.
Example: DB1 is a single copy database present on the server Exch1 and hosts the organization mailbox. The following command can be used to move the organization mailbox to DB2 and make Exch2 the OAB generation server.
The following example creates OAB for address list named “Global Address List FAB” New-Offline Address Book -Name OAB-FAB -Address Lists "Global Address List FAB" The arbitration mailboxes in Exchange Server 2013 are assigned certain “Persisted capability” that defines the purpose/function of the arbitration mailbox.
An arbitration mailbox with Persisted Capability “Organization Capability OABGen” is responsible for OAB generation.
The CAS role maintains log of each request it handles in the log files, present in folder %Exchange Install Path%\Logging\Http Proxy\OAB\ These log files are an excellent tool to identify which mailbox server the CAS chose to serve the request.
Information of some important fields from the log file: The log file can be imported in Excel for better readability.