> > memory in my PC is 16 GB 
> 
> You can safely go to buffer size 100 Mbytes or more.
> 
> > I check the contents of .SHM_TYPE.TXT and it is "POSIXv2_SHM".
> 
> Good.


No, wait, this is all wrong. If it says POSIX shared memory, how come it later
complains about SYSV shared memory and tells you to run SYSV shared memory
commands like ipcrm?!?


> > But there is no buffer sizes in "/Experiment" 


Now this kind of makes sense - you are probably running a strange mixture
of very old and recently new MIDAS. Probably you current version is so old
that it does not use .SHM_TYPE.TXT and can only do SYSV shared memory
and so old it does not have "/Experiment/buffer sizes".

But at some point you must have run a recent version of midas, or you would
not have the file .SHM_TYPE.TXT in your experiment directory.

I say:

a) run the correct ipcrm command (without the spurious "size..." text)
b) review your computer contents to identify all the versions of midas
   and to make sure you are using the midas you want to use (old or new,
   whatever), but not some wrong version by accident (incorrect PATH setting, etc)

As MIDAS developers, we usually recommend that you use the latest version of MIDAS,
certainly latest version is simpler to debug.

K.O.