By default, the list of machines is taken from the db2nodes.cfg file. You can override this by:
If you are running DB2 Extended Enterprise Edition with multiple logical nodes (database partition servers) on one machine, your db2nodes.cfg file will contain multiple entries for that machine. In this situation, the rah command needs to know whether you want the command to be executed once only on each machine or once for each logical node listed in the db2nodes.cfg file. Use the rah command to specify machines. Use the db2_all command to specify logical nodes.
If you specify machines, then rah will normally eliminate duplicates from the machine list, with the following exception:
export DB2NODE=nnn (for Korn shell syntax)
where nnn is the node number taken from the corresponding line in the db2nodes.cfg file, so that the command will be routed to the desired database partition server.
When specifying logical nodes, you can restrict the list to include all logical nodes except one, or only specify one database partition server using the <<-nnn< and <<+nnn< prefix sequences. You may want to do this if you want to run a command at the catalog node first, and when that has completed, run the same command at all other database partition servers, possibly in parallel. This is usually required when running the db2 restart database command. You will need to know the node number of the catalog node to do this. See "Prefix Sequences" for information about the prefix sequences.
If you execute db2 restart database using the rah command, duplicate entries are eliminated from the list of machines. However if you specify the " prefix, then duplicates are not eliminated, because it is assumed that use of the " prefix implies sending to each database partition server, rather than to each machine.