Could you connect via SQL*Net as a user with 'sysoper' privilege
(you'll need a password file and 'grant sysoper to <user>') ?


Also, for your example, check that the 'sticky' bit is set on the user
and group execution bit for the required oracle binaries so that all
processes that run oracle use the same memory

e.g. one of them is this:

-rwsr-s--- 1 oracle dba 69198144 Nov 22 13:12 oracle