Poster is trying to kill zombie opst processes.
This is because sp_opo_wait_msg_delay has a non-zero value.. The message is somewhat misleading: Poster isn't trying to physically kill zombie processes. This message is logged if its call to "alter system kill session <session from a prior incarnation of poster>" doesn't return in the time (in seconds) reflected by the value to which the above SharePlex poster parameter is set.
set param SP_OPO_WAIT_MSG_DELAY 0