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  1. #1
    Join Date
    Feb 2004
    Posts
    2

    Unanswered: Connect to multiple instances of DB2 from a single C Application

    Environment: AIX 5.1, language C, DB2 7.1
    This is what I am trying to do.

    I have more than one instance of DB2 on the server. Need to get the
    list of databases for each instance. The other instances(Nodes) are
    not cataloged in any instance, So I need to connect only through the
    env. variable DB2INSTANCE.

    This is how I am trying to do.
    1. Set environment variable DB2INSTANCE to the first instance.
    2. Attach to the first DB2 instance.
    3. Get the list of databases.
    4. Detach from Instance.
    5. Set environment variable DB2INSTANCE to the Second instance.
    2. Attach to the second DB2 instance.
    3. Get the list of databases.
    4. Detach from Instance.

    The code

    /*Set the environment variables which are used by sqlgetdbs() call to
    * connect to the server to fetch the datbases
    */
    env_value = (char *)malloc(strlen(server)+16);
    strcpy(env_value, "DB2INSTANCE=");
    strcat(env_value, server);

    env_const = (char *)malloc(strlen(env_value)+1);
    strcpy(env_const,env_value);

    if (putenv(env_const) != 0) {
    if (DEBUG) {
    printf("Error setting environment varible DB2INSTANCE\n");
    }
    }
    free(env_value);
    env_var = getenv("DB2INSTANCE");
    printf("env Var set value after: %s\n", env_var);

    /* Attach to the INSTANCE */
    nodename=server;
    sqleatin(nodename, NULL, NULL, &sqlca);
    printf("attach sqlcode %d\n",sqlca.sqlcode);

    instName[SQL_INSTNAME_SZ] = '\0';
    sqlegins (instName, &sqlca);
    printf("ins name sqlcode %d \n", sqlca.sqlcode);
    printf("ins name from sqlegins: %s \n", instName);

    /* open database directory scan */
    sqledosd(dbDirPath, &dbDirHandle, &nbDbEntries, &sqlca);
    /* printf("OPen sqlcode %d\n",sqlca.sqlcode);*/

    /* read the database entries */
    for (dbEntryNb = 0; dbEntryNb < nbDbEntries; dbEntryNb++)
    {
    /* get next database directory entry */
    sqledgne(dbDirHandle, &dbEntry, &sqlca);
    printf("get sqlcode %d\n", sqlca.sqlcode);

    /* printing out the database information on to the screen */
    printf(" database name : %.8s\n", dbEntry->dbname);

    } /* end for */

    /* close database directory */
    sqledcls(dbDirHandle, &sqlca);
    printf("sqlcode close %d \n", sqlca.sqlcode);

    /* Detach from the instance */
    sqledtin(&sqlca);
    printf("sqlcode detach %d \n", sqlca.sqlcode);

    I loop the above peice with a diferrent INSTANCE name.

    THE PROBLEM:
    This works fine for the first INSTANCE but it is fails to connect to
    the second instance and remains connected to the first one.

    Have tried alternate methods using multiple contexts, threads, etc.
    but have not been able to find a solution. This has troubled me for a
    while.
    Any useful information or piece of code that accomplishes this would
    be greatly appreciated.

  2. #2
    Join Date
    Aug 2001
    Location
    UK
    Posts
    4,650

    Re: Connect to multiple instances of DB2 from a single C Application

    I saw this yesterday in Google Answers ... Am I right ? (It had 5 dollars reward against it )

    By any chance do you have the full code (looks like it is missing the include ) ... This will give someone an opportunity to test it and check the problem

    Sathyaram
    Visit the new-look IDUG Website , register to gain access to the excellent content.

  3. #3
    Join Date
    Feb 2004
    Posts
    2
    Yeah, its the same one as in Google answers.

    I had only given the piece of code as this is part of a bigger program.
    Attaching the program file with can by tested .
    Attached Files Attached Files

  4. #4
    Join Date
    Dec 2002
    Posts
    134

    Re: Connect to multiple instances of DB2 from a single C Application

    try using sqleBeginCtx/sqleEndCtx.

    I think your problem is caching of instance variable by DB2. Mentioned above functions will work as a "terminate" equivalent

    BTW, why do you need a C code for such task, you can easily implement a shell script to list all instances/all databases per instance.

    regards,
    dmitri

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