With below error message , my infomix crashed & after restart its working fine. I did not get any error message at OS level ( like volume corruption , disk fail .....) Not even at informix level. All my chunks are OK at OS as well as Informix level.

Is it a BUG ??????? SOLUTION ?????????ANY SUGGESTION ??????

Assert Failed: Buffer modified in inconsistent chunk.
23:23:02 Informix Dynamic Server Version 7.31.FC6XD
23:23:02 Who: Session(671, sapr3@APP11, 18335, 534114856)
Thread(838, sqlexec, 22023ee58, 1)
File: rsdebug.c Line: 936
23:23:02 Results: Chunk 26 is being taken OFFLINE.
23:23:02 Action: Restore chunk from archive. If this is a temporary dbspace
chunk, drop and add the dbspace to enable it.
23:23:45 See Also: /tmp/af.72e547e, shmem.72e547e.0
23:23:45 Error writing '/tmp/shmem.72e547e.0' errno = 22
23:23:45 Assert Failed: Chunk 26 is being taken OFFLINE.
23:23:45 Informix Dynamic Server Version 7.31.FC6XD
23:23:45 Who: Session(671, sapr3@APP11, 18335, 534114856)
Thread(838, sqlexec, 22023ee58, 13)
File: rsmirror.c Line: 1711

I think reserve page of this chunk is corrupt ,
the solution (have to trial) setup another instance then add this chunk (not being primary chunk) for rebuild reserve page so shutdown this instance and start the first instance , if it's the same , you have to config database to skip the dbspace that own this chunk drop/create

Before doing anything, you should check this file:
/tmp/af.72e547e
A lot of information can be found in this file.
For instance, you can see the stack trace of the thread causing the crash.