From FIXwiki

FIX Message DerivativeSecurityListUpdateReport (MsgType=BR)

MsgType	FIX Specification	First introduced	Deprecated
MsgType=BR	PreTrade messages - SecuritiesReferenceData	FIX.5.0

The Derivative Security List Update Report message is used to send updates to an option family or the strikes that comprise an option family.

Message Contents By FIX Version

Notes

Please post comments, clarifications, examples here. Click on the edit button on the right and away you go! 

Don't forget to refer to the FPL Discussion Groups to back up anything you write.
You will often find the authoritative statements on matters of FIX specification interpretation there.
Links from FIXwiki pages to relevant discussions on the FPL site are very valuable.

For example if you were writing a clarification on how to specify the "quantity" of an order in FIX, you might add the
following relevant link, http://www.fixprotocol.org/discuss/read/f5014573, to back up your points.