$Header: /cvsroot/pgsql/src/backend/storage/ipc/README,v 1.3 2003/07/24 22:04:09 tgl Exp $Mon Jul 18 11:09:22 PDT 1988  W.KLASCache invalidation synchronization routines:===========================================The cache synchronization is done using a message queue. Everybackend can register a message which then has to be read byall backends. A message read by all backends is removed from the queue automatically. If a message has been lost because the bufferwas full, all backends that haven't read this message will betold that they have to reset their cache state. This is doneat the time when they try to read the message queue.The message queue is implemented as a shared buffer segment. Actually,the queue is a circle to allow fast inserting, reading (invalidate data) andmaintaining the buffer.