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  1. #1
    Join Date
    Dec 2003
    Posts
    6

    Unanswered: Use chunks from 2 different machines?

    Hi,

    I want to do this:

    We have a main and a backup server (HPUX11), sharing a disk-array containing the chunks (raw devices) of the Informix 7.3 runnig on the main server.

    If the main server crashes (or is down for maintenance) I want to start an informix on the backup machine using the same chunk files that are normally used by the main server. (the device file names for the chunk files will be identical, the hardware paths wont be).

    Has anybody done this before?

    Cheers, Peter

  2. #2
    Join Date
    Jul 2003
    Location
    Calcutta, India
    Posts
    42
    Hi!

    Assuming that the dbspace containing this chunk is not critical, doenot contain logs, and is not rootdbs, whenyou create the dbspace on backup server give this chunk as the chunk name (link) and continue as usual, I hope this will work. I have done something similar, chunk being shared by 2 informixserver residing on the same m/c and the chunk was a cooked file.

    I hope this will work, Thanks
    adityanlal

  3. #3
    Join Date
    Dec 2003
    Posts
    6
    That sounds quite good.
    actually I wanted to go a bit further:
    I simply wanted to use the same onconfig file on both machine. The ROOTPATH points to the 1st chunk of the rootdbs.
    Everything else should be configured in there.

    The spaces will also contain logical logs.
    The spaces will be raw devices.

    Do you think that will make any difference?

    Peter

  4. #4
    Join Date
    Jul 2003
    Location
    Calcutta, India
    Posts
    42
    I don't think that is possible i.e. using the same ROOTDBS by 2 different informix server. This is because the rootdbs contains the critical data and moreover you are placing the logs in rootdbs. Whenever we try to bring up the Informix server, it reads from a file called $INFORMIXDIR/etc/oncfg_<DBSERVER Name>.<DBSERVER Number> which contains the logical log details, checkpoints details and these will be different for 2 different servers. Even if you start (from scratch) with same config. this files will contain different information for 2 different servers.

    Thanks
    adityanlal

  5. #5
    Join Date
    Mar 2003
    Posts
    7

    Re: Use chunks from 2 different machines?

    Hi Peter,

    I have another config. I'm working with Veritas Volume Manager(VVM), think you have to work with something similar to create Volumes for the chunks. With VVM you can export and import Volumegroups, even with a force option, when one server crashes. But using links is ok too.

    You only have to copy once the INFORMIXDIR and when any change is made, do it on both. And take care of starting up both server ;-(

    Cheers
    Christian

  6. #6
    Join Date
    Dec 2003
    Posts
    6
    Christian,
    thanks for the info. We are using the LVM (logical volume manager) that comes with HPUX.

    Adityanlal,
    I am not sure wether we are talking about the same thing. I want to access the chunks alternatively, only one informix up at one time.

    I could not find any $INFORMIXDIR/etc/oncfg_<DBSERVER Name>.<DBSERVER Number> (I think this Informix 9.x?). I only have the "normal" onconfig file. Of course as a Christian said, the onconfig (and the rest of the installation) must be identical on both installations.

    Unfortunnately I cannot test that stuff at the moment, but Ill post it here when I know

    Thank you all,
    Peter

  7. #7
    Join Date
    Apr 2003
    Location
    Phoenix, AZ
    Posts
    177
    You will need to refer to all of your dbspaces/chunks through links so the names are identical for both instances. The link can then point to different locations ie raw logical volumns or devices.
    Fred Prose

  8. #8
    Join Date
    Dec 2003
    Posts
    6
    Hi all,
    as promised my report as to how it went:

    it went fine. After stopping the SERVERA and starting SERVERB
    we importerted the volume groups from the Raid an set them to active.

    Then we had to alter the onconfig file on SERVERB slightly:
    1) Altered the hostname
    2) Altered the number of processors SERVERA had 4 CPUs, SERVERB only 2 CPUs

    Also you have to alter the sqlhosts file to reflect the new hostname.

    As SERVERB had only 256MB of mem (vs. 1024 MB on SERVERA), I used onmonitor to tune down the amount of memory needed by the server.
    No Problem.
    We still can switch easily between the to servers using separate onconfig and sqlhosts files.
    Thx again, all
    Peter

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