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:
- During the export phase, a packet file and a shipping order file are created.
The shipping order file contains delivery instructions for the packet.
- The packet and shipping order are stored in one of the storage bay directories on the synchronization server associated with a Rational® ClearQuest® 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.
- 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.
- 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.