Changing the Master Replica Site
The machine that runs the master replica server must be available at all times. If you are planning to remove this machine from your network or to shut it down for an extended period, you need to change the site of the master replica.
The preferred method for changing the master registry site is to use the dcecp registry designate command to reverse the roles of the master server and a slave server. In other words, make the master the slave and the slave the master.
When you invoke the dcecp registry designate command, the following occurs:
1. The current master sends all pending updates and its propagation queue to the replica designated as the new master.
2. The designated new master reads the current master's replica list to obtain information required for it to manage propagation to the slaves.
3. When the designated new master has obtained all necessary information from the current master, it becomes the new master, and the current master becomes a slave.
Because this orderly and complete transfer of information ensures that no data is lost, the dcecp registry designate command is the preferred method to move the master registry to another machine when the registry servers at the master and slave sites are operating normally. Note that the dcecp registry designate -master command is also available to change a replica from a slave to the master. However, because the dcecp registry designate -master command can cause data to be lost, use it only when the current master has been destroyed. It is not recommended in instances when the master is unreachable because of a network failure or because the master has gone down temporarily.
Follow these steps to change the site of a master replica:
1. Choose the new master site. A slave replica must exist at this site. If necessary, use the dce_config command or your platform's equivalent to configure a slave machine.
2. Issue the Tcl set command to set the default replica to the current master replica. In the following example, the master replica is set to the replica named oddball in the cell giverny.com:
dcecp> set _s(sec) /.../giverny.com/subsys/dce/sec/oddball
dcecp>
3. Issue the registry designate command to reverse the roles of the master and slave. This command takes the name of the replica to be made the new master as an argument. The following example makes the replica named /.../giverny.com/subsys/dce/sec/music the new master:
dcecp> registry designate /.../giverny.com/subsys/dce/sec/music
dcecp>
4. Verify that the master site changed. Do this by issuing the registry show replica command.