I will try to descibe 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
Thank you for your ideas and help.