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Conference turris::digital_unix

Title:DIGITAL UNIX(FORMERLY KNOWN AS DEC OSF/1)
Notice:Welcome to the Digital UNIX Conference
Moderator:SMURF::DENHAM
Created:Thu Mar 16 1995
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:10068
Total number of notes:35879

9613.0. "shm-max set to 4294967296" by SALEM::ARNOLD () Thu Apr 24 1997 13:10

    I have an 8440 with 4 gig of memory that will be running Oracle.
    
    The customer has requested that I modify the /etc/sysconfigtab file
    and set shm-max=4294967296.  When I do this and reboot it shows
    shm-max=0.  I've read notes in this notes file and they said
    that this was QAR'd 33006.  Does anyone know if this has been fixed
    in V4.0b, which I'm running.  I've looked in the QAR database for OSF
    and could not find this QAR.
    
    Thanks for any help that can be provided.
    
    Howard
T.RTitleUserPersonal
Name		DateLines
9613.1shm-max is an int (<= 2GB)ALFAM7::GOSEJACOBFri Apr 25 1997 06:0518
    re .0
    Hmmm, maybe something changed for 4.0x I'm not aware of but as far as I
    know shm-max is limited to 2GB. I just had a look at /usr/include/sys/shm.h
    and yes shmmax in shminfo is an int. So the 2GB limit still holds true.
    
    But, and here's the good news, you don't need to set shm-max larger
    than 2GB. If you want Oracle to allocate a SGA larger than this limit,
    no sweat: the Oracle kernel will automatically allocate as many shared
    memory segments as needed to fit the configured size of the SGA.
    
    BTW. don't forget to add the line:
    
    	vlm_sga_base_address = 0x400000000
    
    in your init.ora parameter file if your SGA is configured larger than 2GB.
    Hope this helps
    
    	Martin
9613.2COMICS::CORNEJWhat&#039;s an Architect?Fri Apr 25 1997 06:1719
    re .1,
    
    Are you sure this is true of all Oracle versions.
    
    A couple of weeks back I helped a customer upgrade from UNIX V3.2C to
    V4.0B.  I don't know which version of Oracle we had (proibably quite
    old) but Oracle UK said it was OK for V4.0B and send a couple of
    patches..
    
    
    After the install,  Oracle refused to start.  I don't have the syntax
    of the messages but it implied not enough memory for the SGA.
    
    We kept upping shm-max until it worked, but when using ipcs we saw that
    the SGA was all in one segment , where in V3.2c it had lots of smaller
    segments.
    
    Jc
9613.3more than 1 segment for quite a whileALFAM7::GOSEJACOBFri Apr 25 1997 08:0313
    re .2
    I'm sure as far as I can remember back and that would be 7.1.3. What
    version of Oracle did the customer use? When they upgraded to 4.0B
    where there any shared memory related sysconfitab parameters left over
    e.g. gh-chunks? Was new-wire-method set to 0?
    
    There's also a little tool that comes with the Oracle installation,
    at no extra charge :-). Try a 'tstshm' when logged in as the Oracle
    owner. The output will tell you what the tool tried to allocate
    shared segment wise.
    
    	Martin