IDS startup problem (from offline to quiescent)

We can not bring our IDS into quiescent mode. After Linux server restart we run onmonitor (Mode, Startup) and the rusult is the the mode is not changed to quescent but no error message is shown. If we look in online.log there is a line "Quiescent Mode". Isn't it strange? Notes: We have IDS 7.3.

In detail what happend after restart.
1) we make: export INFORMIXSERVER=imc05
2) we tried onstat with result: shared memory not initialised for INFORMIXSERVER 'imc05'
3) we tried ipcs with result no shared memory shown
4) we make onmonitor -> Mode -> Startup
message was "Initialising, please wait ..."
after several seconds we get message: "Press return to continue"
after we press return we get message: "shared memory not initialised for INFORMIXSERVER 'imc05'"
we exit onmonitor
5) we tried onstat with result: shared memory not initialised for INFORMIXSERVER 'imc05'
6) we tried ipcs with result: 4 shared memory segments are listed, one of them was "locked" - key: 0x52564801

Please help!