Richard,

If You have only 1 GB of physical RAM, both settings should be OK.

The problem is when You have 2 or 4 GB and try to allocate to Informix
as much shared memory as possible.

The problem with Linux is that, by default, it attaches shared libraries
to the process at starting address 0x40000000 (that is, 1GB).
If You want to allocate more then 1GB to Informix, You should set
SHMBASE above this value, e.g. 0x50000000 or even 0x44000000.

Linux allows to address 3GB of memory per process (upper 1 GB is reserved
for internal use). That is, You can allocate almost 2 GB of shared memory to
Informix.

The other trick is that Linux kernels 2.4.19 and higher support so-called
MAPPED_BASE feature. If You have a kernel with MAPPED_BASE, You can
relocate the address at which shared libraries are attached (for all
children
of particular shell process). In that case, You can lower SHLIB initial
address and set proper SHMBASE to allocate up to 3GB of shared memory
to Informix engine.

Best regards,
Alexey



>It's fine. SHMBASE is the initial attach address for shared memory within
>the engine. Higher is USUALLY OK and if it were going to cause a problem
it
>would have already.

>Art S. Kagel

>> Dear Informixers,
>>
>> I've been running IDS WE 7.31UD5 (3 instances) on a SuSE 7.2 Linux system
>> (Kernel 2.4.18-64GB-SMP) with 1GB physical memory without problems for
>> several years. The current configuration has been running for a year.
>>
>> During a review of my ONCONFIG parameters, I just discovered that SHMBASE
is
>> not set according to the release notes on all of my instances. Instead of
>> the standard 0x10000000L, it is set to 0x20000000 (note the absence of
the
>> "L"). Unfortunately and most embarrassingly for me, I could find no
>> documentation of why and when I made this change.
>>
>> Since everything is running smoothly, I am not too worried. Or should I
be?
>> Should I reset the parameter to the standard?
>>
>> Regards, Richard
>>
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