Is it - AFBufferOption.BufferIfPossible?
But I thought that was the default value.
AF SDK Buffering to PI Server/Collective utilizes PI Buffer Subsystem. If security is configured for the PI Buffer Subsystem then by default the data writes will be buffered.
Please download and install PI AF Developer Tools 2014 from PI Asset Framework category at vCampus Download Center. You will find AF SDK Reference (AFSDK.chm) at %PIHOME%\Help\. In the "Contents" page, please check the "AF SDK Buffering" section (under "AF SDK Reference") . There are also examples in some of the buffering -related methods in that AFSDK.chm file.
There is an overload for PIPoint.UpdateValues method from PI AF SDK 2.6 whose third parameter is an OSIsoft.AF.Data.AFBufferOption object which refers to an enumeration value that specifies buffering option.
If you take a look at the PI AF Developer Tools, as suggested by Eddy, you will read the following remark:
"For successul update through Buffer, this method requires that PI Buffer Subsystem needs to be correctly pre-configured with PI Buffer Manager.
Update through Buffer will be fanned to Collective members."
Hope it helps!!