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WebLogic Frequently Asked Questions: WebLogic jDriver for Oracle

- Unsatisfied link error

- Error using FOR UPDATE statement with Oracle 8

- OCIW32.DLL error

- Doesn't the WebLogic jDriver for Oracle driver support all of the transaction isolation levels?

- Using multibyte character sets with WebLogic jDriver for Oracle

- How do I use OS authentication with WebLogic jDriver for Oracle and WebLogic JDBC connection pools?

- What type of Object is returned by ResultSet.getObject()?

- How do I limit the number of Oracle database connections?

- How can I call Oracle stored procedures that take no parameters?

- How do I bind String values in a PreparedStatement?

- Using 8-bit character sets with Oracle/Solaris

- How do I know what codesets I have available in Oracle?

- What do I do with an "ORA" SQLException?

- What does the error "ORA-6502" mean?

- Why would I get an error while trying to retrieve the text for ORA-12705?

- When I update my database using Oracle database link I run out of resources

Unsatisfied link error

Why do I receive the following error message when trying to use the WebLogic jDriver for Oracle: java.sql.SQLException: System.loadLibrary threw java.lang.UnsatisfiedLinkError with the message 'no weblogicoci36 in java.library.path'?

WebLogic jDriver for Oracle is of type 2 which requires a native component. The native component comes as a linked library named weblogicoci3x.dll on Windows NT or libweblogicoci3x.so (or .sl, .dll, etc., depending on the operating system) on Solaris. The linked library must be located somewhere that the operating system will look when an application needs it. WebLogic has an internal variable called java.library.path. This variable corresponds to an environment variable that you set in the shell where you run WebLogic. On Windows NT, the java.library.path corresponds to the PATH environment variable.

At boot-time of the server, WebLogic reads in the values from PATH (for example, c:\winnt;d:\weblogic\bin) and sets these values as equal to the java.library.path internally. On Solaris, Linux and TruUnix, the environment variable is called LD_LIBRARY_PATH, on HPUX it is called SHLIB_PATH and on IBM's AIX it is called LIBPATH. The value that is read into the internal variable java.library.path is the environment variable that you specify at the time WebLogic starts. The java.library.path is where WebLogic looks for the shared library files that it needs to access the database.

On some UNIX platforms, if a call requires library A, the loader does not find and load library A and the loader makes the required native call, and if the native call requires library B and library B is not found, the linker will sometimes say that the top-level library A was not found. For the WebLogic jDriver, library A is libweblogicoci36 and library B might be Oracle's OCI client libs or, below that, it might be Sun's standard C libraries.

To avoid getting the UnsatisfiedLinkError:

- Do not rename libweblogicoci36.so or libweblogicoci36.sl to weblogicoci36.

- Specify the correct path that WebLogic will use to look for the shared library files that it needs to access the database.

- Ensure that you have Oracle's client installed on your machine and that you have Oracle's libraries and the standard C libraries in your LD_LIBRARY_PATH

- Ensure that you have $ORACLE_HOME set to point to the root of your oracle installation, as the Oracle install indicates.

- Ensure that ORACLEHOME/version/lib is in your java.library.path. Your ORACLE_HOME variable must be set even if you are feeding values directly into the java.library.path. For example, if you are going to use the 7.3.4 libraries and your Oracle installation is at /oracle, you need /oracle/7.3.4/lib in your java.library.path.

  - For Windows NT/2000:

    /weblogic/bin and /weblogic/bin/client_library_version (for example, /weblogic/bin/oci734_7) + ORACLE_HOME/version/lib

  - For Solaris:

    /weblogic/lib/solaris and /weblogic/lib/solaris/client_library_version (for example, /weblogic/lib/solaris/oci734_7) + ORACLE_HOME/version/lib

  - For HPUX11:

    /weblogic/lib/solaris and /weblogic/lib/solaris/client_library_version (for example, /weblogic/lib/hpux11/oci734_7)+ ORACLE_HOME/version/lib

- If you are using HPUX 10, you must move to HPUX 11 to use type 2 Oracle drivers with WebLogic Server 5.1.

- If you have ensured all of the above and you still get the UnsatisfiedLinkError:

- You may be specifying improper directories or the files may be corrupted. Run the FILE command on UNIX to assure file integrity.

- Ensure that WebLogic has read and execute permissions on the shared library files.

- Rearrange the order of the paths that you specify for the weblogic.library.path variable trying all possible combinations.

- Put /usr/lib in your java.library.path and add standard C libraries.

- As a last resort, reinstall WebLogic Server, your operating system and your Oracle libraries.

Error using FOR UPDATE statement with Oracle 8

Why have I been receiving the following error message from my Oracle 8 server when using a FOR UPDATE statement: ORA-01002: fetch out of sequence?

There is a problem in the Oracle 8 server that causes this error when using a FOR UPDATE statement with AUTOCOMMIT turned on (which is the default state when using JDBC). This is known to happen on Oracle 8.0 and 8.1 on Solaris and on Oracle 8.1 on Windows NT. If you turn AUTOCOMMIT off, you will not receive this error. Since this problem is due to a change in the Oracle 8 server, you should contact Oracle support for more information.

OCIW32.DLL error

I have been receiving the following error message when using your JDBC driver for Oracle: "The ordinal 40 could not be loaded in the dynamic link library OCIW32.dll"

This problem is caused by an out-of-date version of OCIW32.DLL in your system directory. Some programs install this file in the system directory in order to run. If you remove this file from the system directory you should no longer receive this error.

Doesn't the WebLogic jDriver for Oracle driver support all of the transaction isolation levels?

Our servlet application uses the Oracle JDBC thin drivers to access a database that includes BLOB fields. We installed WebLogic jDriver for Oracle and the same code fails with the following exception:

       com.roguewave.jdbtools.v2_0.LoginFailureException:
       TRANSACTION_READ_UNCOMMITTED isolation level not allowed
         The Stack Trace:
       com.roguewave.jdbtools.v2_0.LoginFailureException:
       TRANSACTION_READ_UNCOMMITTED isolation level not allowed
         at com.roguewave.jdbtools.v2_0.jdbc.JDBCServer.createConnection
         (JDBCServer.java :46)
         at com.roguewave.jdbtools.v2_0.ConnectionPool.getConnection_
         (ConnectionPool.jav a:412)
         at com.roguewave.jdbtools.v2_0.ConnectionPool.getConnection
         (ConnectionPool.java :109)

We set the Isolation_level to 1 in our code that calls the RogueWave JDBCServer class. This works with the Oracle thin driver but fails with WebLogic jDriver for Oracle. Any clues?

WebLogic jDriver for Oracle supports the following transaction isolation levels:

       SET TRANSACTION ISOLATION LEVEL READ COMMITTED
       SET TRANSACTION ISOLATION LEVEL SERIALIZABLE

According to the Oracle documentation, the Oracle DBMS only supports these two isolation levels. Unlike other JDBC drivers, WebLogic's drivers throw an exception if you try to use an isolation level that is unsupported. Some drivers silently ignore attempts to set an unsupported isolation level. WebLogic suggests testing whether the Oracle thin driver is not just ignoring settings for unsupported isolation events.

Using multibyte character sets with WebLogic jDriver for Oracle

I am having trouble using Unicode codesets with the WebLogic jDriver for Oracle driver. How can I use a codeset in my Oracle database with the WebLogic JDBC drivers?

There are two important things you must do to use Unicode codesets:

1. You must install the appropriate codeset when you install Oracle. If you did not do this in the original installation, you will need to re-run the Oracle installer and install the proper codeset.

2. You must define the NLS_LANG variable in the environment where the JDBC driver is running. You can do this by assigning the proper codeset to NLS_LANG in the shell from where you start the WebLogic Server.

The Developers Guide has more information about internationalization support. For general information about Unicode see the Unicode website. For a list of Unicode language abbreviations, see the JavaSoft website.

How do I use OS authentication with WebLogic jDriver for Oracle and WebLogic JDBC connection pools?

I'd like to set up a WebLogic JDBC connection pool so that it uses the authentication associated with the user who is running my client application. I'm using WebLogic jDriver for Oracle. How can I do that?

Using OS authentication in connection pools essentially means that you are using the userid of the user that started the WebLogic Server. This means that database security will rely strictly on the security of WebLogic; that is, if you are allowed to make a client connection to the WebLogic Server and access the pool, then you can get to the database.

You can do this with WebLogic jDriver for Oracle because Oracle uses the process owner to determine who is attempting the connection. In the case of WebLogic JDBC, this is always the user that started the WebLogic Server.

To set up your Oracle instance to use this feature, your DBA needs to follow these basic steps. The full procedure is described in more detail in your Oracle documentation.

1. Add the following line to the INIT[sid].ORA file:

         OS_AUTHENT_PREFIX = OPS$

   Note that the string "OPS$" is arbitrary and up to the DBA.

2. Log in to the Oracle server as SYSTEM.

3. Create a user named OPS$userid, where userid is some operating system login ID. This user should be granted the standard privileges (for example, CONNECT and RESOURCE).

Once the userid has been set up, you can connect with WebLogic jDriver for Oracle by specifying "/" as the username property and "" as the password property. Here is an example for testing this connection with the dbping utility:

     $ java utils.dbping ORACLE "/" "" myserver

Here is a code example for WebLogic jDriver for Oracle:

      Properties props = new Properties();
      props.put("user",       "/");
      props.put("password",   "");
      props.put("server",     "myserver");

      Class.forName("weblogic.jdbc.oci.Driver").newInstance();
      Connection conn =
        DriverManager.getConnection("jdbc:weblogic:oracle", props);

Here is how you set up the registration of a connection pool (this one named "eng") for use with this system:

    weblogic.jdbc.connectionPool.eng=\
            url=jdbc:weblogic:oracle,\
            driver=weblogic.jdbc.oci.Driver,\
            initialCapacity=4,\
            maxCapacity=10,\
            capacityIncrement=2,\
            props=user="/";password="";server=myserver
    weblogic.allow.reserve.weblogic.jdbc.connectionPool.eng=guest,joe,jill

The second property sets up an access control list for this connection pool and gives the users "guest," "joe," and "jill" the same database privileges as the user that started the WebLogic Server.

What type of Object is returned by ResultSet.getObject()?

I am confused about what type of object will be returned by the ResultSet.getObject() method. What can I expect if my database column is a NUMBER(16,4), or just NUMBER?

WebLogic jDriver for Oracle always returns a Java object that will preserve the precision of the data retrieved. With Release 2.5 and later, WebLogic jDriverWebLogic jDriver for Oracle returns the following from the getObject() method:

- For columns of types NUMBER(n) and NUMBER(m,n): we return a Double if the defined precision of the column can be represented by a Double; otherwise we return BigDecimal.

- For columns of type NUMBER: Because there is no explicit precision, we determine the Java type to return based on the actual value in each row, and this may vary from row to row. We will return an Integer if the value has a zero-valued fractional component and the value can be represented by an integer.

For example, 1.0000 will be an integer. We will return a long for a value such as 123456789123.00000. If a value has a non-zero fractional component we return a Double if the precision of the value can be represented by a Double; otherwise we return a BigDecimal.

How do I limit the number of Oracle database connections?

I want to limit the number of Oracle database connections generated by the WebLogic Server in response to client requests. How would I do this?

If you want to limit the number of database connections used by the WebLogic Server, you can use connection pools. Connection pools allow T3 applications to share a fixed number of database connections. For more information on how to set up connection pools, see the Developers Guide, Using WebLogic JDBC.

How can I call Oracle stored procedures that take no parameters?

I'm working with the CallableStatement methods for the WebLogic jDriver for Oracle driver and having trouble calling an Oracle procedure that has no parameters. How can I call a stored procedure with no parameters from Java?

Here is what we use that works:

      CallableStatement cstmt = conn.prepareCall("Begin procName; END;");
      cstmt.execute();

where procName is the name of an Oracle stored procedure. This is standard Oracle SQL syntax that works with any Oracle DBMS. You might also use the following syntax:

     CallableStatement cstmt = conn.prepareCall("{call procName};");
      cstmt.execute();

This code, which conforms to the Java Extended SQL spec, will work with any DBMS, not just Oracle.

How do I bind String values in a PreparedStatement?

I'm using WebLogic jDriver for Oracle. I cannot get the PreparedStatement class to bind Strings in a statement. The setString() method doesn't seem to work. Here is how I set up the PreparedStatement:

      String pstmt = "select n_name from n_table where n_name LIKE '?%'";
      PreparedStatement ps = conn.prepareStatement(pstmt);
      ps.setString(1, "SMIT");
      ResultSet rs = ps.executeQuery();

You can't bind a value into another value in a PreparedStatement. The complete value needs to be specified in a String (without using embedded quotes) and then bound to an unquoted question-mark (?). Here is the corrected code:

      String matchvalue = "smit%";
      String pstmt = "select n_name from n_table where n_name LIKE ?";
      PreparedStatement ps = conn.prepareStatement(pstmt);

      ps.setString(1, matchvalue);
      ResultSet rs = ps.executeQuery();

Using 8-bit character sets with Oracle/Solaris

I'm using WebLogic jDriver for Oracle on Solaris with an 8-bit character set, but I'm not seeing the characters I expect. What's the problem?

If you are using an Oracle database with an 8-bit character set on Solaris, make sure you set NLS_LANG to the proper value on the client. If NLS_LANG is unset, it defaults to a 7-bit ASCII character set, and tries to map characters greater than ASCII 128 to a reasonable approximation (for example, &aacute;, &agrave;, &acirc; would all map to a). Other characters are mapped to a question mark (?).

How do I know what codesets I have available in Oracle?

When I am using the WebLogic jDriver for Oracle driver with my Oracle database, how can I find out what foreign language codesets I can access and use?

To find out what codesets you currently have available in Oracle, execute the following SQL query from SQLPlus at the command line:

     SQL> SELECT value FROM v$nls_valid_values
              WHERE parameter='CHARACTERSET';

The response will be a listing of all of the codesets currently installed on your system. This listing will look something like the following shortened list:

      VALUE
      -----------------------------------------------------------
      US7ASCII
      WE8DEC
      WE8HP
      US8PC437
      WE8EBCDIC37
      WE8EBCDIC500
      WE8EBCDIC285
      ...

If you want to constrain the value in the query to a specific codeset you are searching for, you might use a SQL query like the following:

     SQL> SELECT value FROM v$nls_valid_values
              WHERE parameter='CHARACTERSET' and VALUE='AL24UTFFSS';

This would produce the following response if the codeset is installed:

      VALUE
      -------------------------------------------------------------
      AL24UTFFSS

Additional codesets can be added using Oracle's installation tools. Contact Oracle for more information.

What do I do with an "ORA" SQLException?

I am having a problem with my WebLogic jDriver for Oracle application that is producing a SQLException. There is an Oracle ID number in it that I do not recognize. How do I look this up? Here is an example:

      java.sql.SQLException: ORA-12536: TNS: operation would block

You can look up an Oracle error by using the oerr command. For example, the description of error ORA-12536 can be found with the command:

     > oerr ora 12536

What does the error "ORA-6502" mean?

I'm using WebLogic jDriver for Oracle. I'm getting the error "ORA-6502: value or numeric error" as the result of a stored procedure, using a CallableStatement. What does this mean?

The default length of a string bound to an OUTPUT parameter of a CallableStatement is 128 characters. If the value you assign to the bound parameter exceeds that length, you will get this error.

You can adjust the length of the value of the bound parameter by passing an explicit length with the scale argument to the CallableStatement.registerOutputParameter() method.

Why would I get an error while trying to retrieve the text for ORA-12705?

I'm using WebLogic jDriver for Oracle and getting the following error:

    Error while trying to retrieve text for error ORA-12705

What does this mean?

This error occurs when you have not set the ORACLE_HOME environment variable properly - a common mistake. In order to use WebLogic jDriver for Oracle, the Oracle client software needs to be installed and ORACLE_HOME must be set.

You may also see this error message if you try to use WebLogic jDriver for Oracle's internationalization capabilities with a language/codeset combination that is not installed on your system. If you get the ORA-12705 error with the correct error text, then either you have set NLS_LANG improperly, or you do not have the right codesets installed on your system.

When I update my database using Oracle database link I run out of resources

When I use Oracle's database link to update my database, temporary table locks are created and the server runs out of resources. The error I get is "maximum number of temporary table locks exceeded". I'm careful to close my result sets and statements when I've finished. What is going on?

The database link is an object in the local database that allows you to access tables, views, and such in a remote database. The database link is controlled by the Oracle server, so the driver has no control over its use of resources. What happens is the link appears to perform the commit (since other processes could see the records that were being created) but it doesn't free any resources until the connection is closed. The solution is to remove the database link and use the JDBC driver to do your selects, inserts, and updates.

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