Alternative Architectures

• Page Server (PS) - The Call Back Read Algorithm.
  • Read request is sent to server (if no local copy) :
    Server sends the page back to the requesting client, if no write lock else wait for release. If there exists a local copy then a local read is performed.
  • Write request to server.
    • Call Back request to all clients who have the page.
    • Client waits for R-Lock release, purges page, releases lock to server.
    • After all callbacks finish, server grants lock to client.
    • At EOT client releases W-Lock to server, retains R-only copy.