I was browsing connection information in master..sysprocesses on my SQL Server 2000 server and noticed some connections in the net_library column that have the value LPC. I've installed named pipes and TCP/IP as valid Net-Libraries. What is LPC, and how did it get in the net_library column?
LPC stands for local procedure call; it's the Net-Library that's based on shared-memory communications and that a client and SQL Server use for efficient communications when both processes are running on the same machine. SQL Server Books Online (BOL) is usually a wonderful reference, but it doesn't contain any reference to LPC. You get an LPC connection from client to server by default when you connect to SQL Server from a local client, as long as you don't use a client alias that defines a particular Net-Library. When you have an LPC connection, the net_library column in the master..sysprocesses table for your connection will have the value LPC.
Learn more from "Download SQL Server 2000 via ServerNet II Net-Library" and "Calling a Stored Procedure from Another Stored Procedure."