Following yesterdays theme of handy but less well known opmnctl commands, here's another one I like.
If you want to start the processes OPMN is configured to manage on a sequential basis (ie one process is started and completes its startup before the next one) then you can use the command below.
$opmnctl startproc sequential=true
The usage text describes it succinctly as:
$opmnctl usage startproc
If the value of the sequential attribute is "true", each process or application targetted by the request will be acted upon sequentially (one at a time). The request order of affected managed-process dependencies will be honored.