There seems to be no information on this program anywhere, so for anyone who gets a problem with it. Here's the answer from IBM.
"db2pgixt.exe is DB2 calls to interface with the user exit program, which performs archive log/ backup."
In my case it was using 100% of cpu as I was archiving logs to TSM and TSM was not available. As soon as TSM came back up, the problem went away.
I hope this helps anyone else who gets this problem.