The MultiSite store-and-forward facility (the shipping server) is a file-transfer service that automates the transport phase of replica creation and synchronization. It can handle packets of any size (up to the maximum packet size specified in the shipping.conf file on Linux™ and the UNIX™ system or the MultiSite Control Panel on Windows™), can route files through a series of MultiSite hosts (one hop at a time), and includes support for handling data-communications failures.

This is how the store-and-forward process works:
  1. During the export phase, a packet file and a shipping order file are created. The shipping order file contains delivery instructions for the packet.
  2. The packet and shipping order are stored in one of the storage bay directories on the VOB replica host or on the synchronization server associated with a HCL Compass database replica.

    If the packet is associated with a storage class, the packet is stored in the storage bay specified by the storage class. You can define storage classes in the shipping.conf file on Linux and the UNIX system and the MultiSite Control Panel on Windows.

  3. The shipping server uses the instructions in the shipping order to transfer the packet file from the storage bay at the local site to the corresponding bay on a host at another site.
  4. If necessary, the shipping server on the receiving host sends the packet to its next destination.

Packet transport

An explicit command, manual or automated, invokes the shipping server on the sending host. The shipping server process contacts the albd_server process on the receiving host, which in turn invokes the shipping server on the receiving host in receive mode. After a TCP/IP connection has been established between the sending and receiving invocations of the shipping server, the file is transferred.