4.3 Notes on Different Transport Methods

If your sites have a high-speed connection, you can take advantage of the MultiSite store-and-forward facility when you create a new replica. If your current site does not have IP connectivity to the site of the new replica, you can use a file-based packet transfer method (for example, ftp or email).

Store-and-Forward Method

The following sections describe issues you must consider when you use the store-and-forward method.

Communication Between Replica Hosts

The hosts must be able to communicate with each other. If your network uses host names, the sending host must be able to resolve the receiving host's name to an IP address. To accomplish this, you may have to update the hosts file, hosts NIS map, or Domain Name Service. Verify TCP/IP access by using rcp on each host to access the other hosts.

NOTE: If hosts in your network are known only by their IP addresses, you can use the IP addresses instead of host names, and no resolution is necessary.

Limiting the Size of a Packet

The mkreplica command fails if it tries to create a packet larger than the size supported by your system. To prevent this problem and improve reliability, use the -maxsize option to divide the replica-creation packet into multiple packets:

multitool mkreplica -export -maxsize 1g ...

For information about default packet size limits, see the mkreplica reference page.

Transport Options

When you enter the mkreplica -export command, you can use either the -fship option to send the packet immediately, or the -ship option to store the packet in the outgoing shipping bay. With -ship, you must invoke the shipping_server to send the packet.

The outgoing packet is stored in the outgoing subdirectory of a storage bay. By default, mkreplica uses the default storage bay (ccase-home-dir/shipping/ms_ship on UNIX and ccase-home-dir\var\shipping\ms_ship on Windows).

The incoming and outgoing subdirectories of storage bays contain packets waiting for transport or processing. All shipping operations look for packets in these subdirectories. At the receiving site, the incoming packet is stored in the incoming subdirectory of a storage bay.

Notes on Using Tape or a File-Based Transfer Method

When you use the -tape option (UNIX) or a file-based method for transport, you may need to use the -maxsize option to prevent the tape from filling up or to make sure the file is a manageable size. In this example, the administrator writes the replica-creation packet to tape, using the -maxsize option. The mkreplica command prompts for additional tapes if necessary.

MINUTEMAN% multitool mkreplica -export -work /usr/tmp/wk -tape /dev/tape \
-maxsize 75m goldengate:sanfran_hub@/vobs/dev
Enabling replication in VOB.
Comments for "sanfran_hub":
First time replication for dev VOB; Creating new replica, sanfran_hub, on host goldengate
.

Please insert a tape to hold packet number 1.
When ready, enter `proceed' (proceed/abort) [proceed] <RETURN>
Generating packet number 1...
Dumping database...
. . .
Dumper done.