Installing DB2 Express C on linux

By Confusion on Saturday 20 June 2009 15:43 - Comments (2)
Category: Software engineering, Views: 5.438

For anyone else trying to install DB2 Express C, the free community edition of IBM's DB2, on his linux system and running into problems:
  • You need to source sqllib/db2profile in every shell where you are going to run commands from sqllib/bin:
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    confusion@ulm:~$ . sqllib/db2profile

  • Running the db2val validation program multiple times in a row can yield different results. For instance, on the first attempt, it told me it couldn't find the sqllib/logs directory. However, that one was already present (perhaps created by db2val?) and when I ran the validation program again, it noticed that.
  • If db2val fails to start your instance with
    SQL1220N The database manager shared memory set cannot be allocated.
    then you probably need to increase the maximum amount of shared memory the kernel may allocate:
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    sysctl -w kernel.shmmax=268435456


    The default is 32M and this increases it to 256M, which turned out to be enough. For 64-bit systems, they advise pushing it to 1GB.

    Edit: As moto-moi points out in the comments, this is a temporary change that will disappear with a reboot. To make it permanent, follow his instructions.
  • If running
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    confusion@ulm:~$ sqllib/adm/db2start

    returns
    SQL10007N Message "-1390" could not be retrieved. Reason code: "3".
    then you probably forgot the first step I described here.
  • If you try to make a connection from your favorite programming language and you receive
    ROOT CAPABILITY REQUIRED
    then you probably did a non-root install. Unfortunately, DB2 doesn't have any DB-level users: all user management, including authentication, is delegated to the OS. On a *nix system, the routine checking the password usually requires root privileges. The problem is that the file sqllib/security/db2ckpw needs to be owned by root and needs to have its setuid bit set:

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    chown root db2ckpw
    chmod u+s db2ckpw


    I first found the file sqllib/security32/db2ckpw, but that doesn't seem to be used on linux. Might be the Windows version? Afterwards, perform a

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    db2 force applications all
    db2stop
    db2start


    The first command breaks all connections, otherwise the db2stop probably won't work.
  • Keep an eye on sqllib/db2dump/db2diag.log: that's where interesting logging about DB2's functioning ends up. The db2diag command can be used to extract information from that file and can be used to tail it, if you haven't done so already.
  • A warning I encountered in the db2diag log was
    The user per process file descriptor limit of 1024 is less than the maxfilop setting of 30720
    This can be solved by issuing

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    ulimit -n 32768


    However, that usually won't work, as the default limits prevent you from going above 1024. To overcome that limit, add the following line to /etc/security/limits.conf

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    your_db2_user hard nofile 32768


    After that, you need to open a new shell (for that user) (if you are running an X environment: restart X) and the new shell will have it maximum number of file descriptors set to 32768 after you issue the ulimit command. Now all you need to do is restart DB2.

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Comments


By Tweakers user Recursio, Saturday 20 June 2009 16:31

Thanx! Quite helpful. :)

By Tweakers user moto-moi, Saturday 20 June 2009 18:26


code:
1
sysctl -w kernel.shmmax=268435456


You would be better of to add this line to /etc/sysctl.conf and run sysctl -p /etc/sysctl.conf, that way you are sure the value is correct and it is also used the next time you restart the machine.

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