6 Features Specific to JDBC OCI Driver

Benefits of Client Result Cache

The benefits of the OCI client-side result set cache are the following:

• The JDBC OCI client-side result set cache is completely transparent to OCI applications and its cache of result set data is kept consistent with any session or database changes that affect its result set.

• Since the result cache is on the client-side, a cache hit causes SQL query execute and fetch calls to be processed locally, instead of making server round trips. This can result in huge performance savings for server resources, for example, server CPU and server I/O.

• The result cache on JDBC OCI client is per-process, so multiple client sessions can simultaneously use matching cached result sets.

• The result cache on JDBC OCI client minimizes the need for each OCI application to have its own custom result set cache.

• The result cache on JDBC OCI client uses OCI client memory that is cheaper than server memory.

Usage Guidelines in JDBC

You can enable result caching in the following two ways:

• RESULT_CACHE_MODE Parameter

• Table Annotations

• SQL Hints

CREATE|ALTER TABLE [<schema>.]<table> ... [RESULT_CACHE (MODE {FORCE|DEFAULT})]

CREATE TABLE foo (a NUMBER, b VARCHAR2(20)) RESULT_CACHE (MODE FORCE);

ALTER TABLE foo RESULT_CACHE (MODE DEFAULT);

String  query  = "select /*+ result_cache */ * from emp where empno < : 1";
   ((oracle.jdbc.OracleConnection)conn).setImplicitCachingEnabled(true);
   ((oracle.jdbc.OracleConnection)conn).setStatementCacheSize(10);
   PreparedStatement  pstmt;
   ResultSet rs;
     
    for (int j = 0 ; j < 10 ; j++ )
    {
       pstmt  = conn.prepareStatement (query);
       pstmt.setInt(1,7500);
       rs  = pstmt.executeQuery();
         while (rs.next( ) )
        {     // see the values  }
          rs.close;
          pstmt.close( ) ;
        }
    } 

ALTER TABLE dept result_cache (MODE FORCE);

Overview of Instant Client

The Instant Client feature makes it extremely easy to deploy OCI, Oracle C++ Call Interface (OCCI), Open Database Connectivity (ODBC), and JDBC-OCI based customer applications, by eliminating the need for an Oracle home. The storage space requirement of a JDBC OCI application running in the Instant Client mode is significantly reduced compared to the same application running on a full client-side installation. The Instant Client shared libraries occupy only about one-fourth the disk space used by a full client installation.

Table 6-1 shows the Oracle client-side files required to deploy a JDBC OCI application. Library names of release 11.2 are used in the table. The number part of library names will change in future releases to agree with the release.

Benefits of Instant Client

The benefits of Instant Client are the following:

• Installation involves copying a small number of files.

• The number of required files and the total disk storage on the Oracle client-side are significantly reduced.

• There is no loss of functionality or performance for applications deployed with the Instant Client.

• It is simple for independent software vendors to package applications.

JDBC OCI Instant Client Installation Process

The Instant Client libraries can be installed by choosing the Instant Client option from Oracle Universal Installer. The Instant Client libraries can also be downloaded from the Oracle Technology Network Web site. The installation process is as follows:

1. Download and install the Instant Client shared libraries and Oracle JDBC class libraries to a directory, such as instantclient.

2. Set the library path environment variable to the directory from Step 1. For example, on UNIX systems, set the LD_LIBRARY_PATH environment variable to instantclient. On Microsoft Windows, set the PATH environment variable to locate the instantclient directory.

3. Add the full path names of the JDBC class libraries to the CLASSPATH environment variable.

After completing these steps you are ready to run the JDBC OCI application.

The JDBC OCI application operates in the Instant Client mode when the OCI and JDBC shared libraries are accessible through the library path environment variable. In the Instant Client mode, there is no dependency on the ORACLE_HOME and none of the other code and data files provided in ORACLE_HOME is needed by JDBC OCI, except for the tnsnames.ora file.

Instant Client can be also installed from Oracle Universal Installer by selecting the Instant Client option. The Instant Client files should always be installed in an empty directory. As with the OTN installation, you must set the LD_LIBRARY_PATH environment variable to the Instant Client directory to operate in the Instant Client mode.

If you have done a complete client installation by choosing the Admin option, then the Instant Client shared libraries are also installed. The location of the Instant Client shared libraries and JDBC class libraries in a full client installation is:

On Linux or UNIX systems:

• libociei.so library is in $ORACLE_HOME/instantclient

• libclnstsh.so.11.2, libocijdbc11.so, and libnnz11.so are in $ORACLE_HOME/lib

• The JDBC class libraries are in $ORACLE_HOME/jdbc/lib

On Microsoft Windows:

• oraociei11.dll library is in ORACLE_HOME\instantclient

• oci.dll, ocijdbc11.dll, and orannzsbb11.dll are in ORACLE_HOME\bin

• The JDBC class libraries are in ORACLE_HOME\jdbc\lib

By copying these files to a different directory, setting the library path to locate this directory, and adding the path names of the JDBC class libraries to the CLASSPATH environment variable, you can enable running the JDBC OCI application in the Instant Client mode.

Usage of Instant Client

Instant Client is a deployment feature and should be used for running production applications. For development, a full installation is necessary to access demonstration programs and so on. In general, all JDBC OCI functionality is available to an application being run in the Instant Client mode, except that the Instant Client mode is for client-side operation only. Therefore, server-side external procedures cannot operate in the Instant Client mode.

Patching Instant Client Shared Libraries

Because Instant Client is a deployment feature, the emphasis has been on reducing the number and size of files required to run a JDBC OCI application. Therefore, all files needed to patch Instant Client shared libraries are not available in an Instant Client deployment. An ORACLE_HOME based full client installation is needed to patch the Instant Client shared libraries. The opatch utility will take care of patching the Instant Client shared libraries.

After applying the patch in an ORACLE_HOME environment, copy the files listed in Table 6-1, "OCI Instant Client Shared Libraries" to the instant client directory as described in "JDBC OCI Instant Client Installation Process".

Instead of copying individual files, you can generate Instant Client ZIP files for OCI, OCCI, JDBC, and SQL*Plus as described in "Regeneration of Data Shared Library and ZIP files". Then, you can copy the ZIP files to the target computer and unzip them as described in "JDBC OCI Instant Client Installation Process".

The opatch utility stores the patching information of the ORACLE_HOME installation in libclnstsh.so.11.2. This information can be retrieved by the following command:

genezi -v

Note that if the computer from where Instant Client is deployed does not have the genezi utility, then it must be copied from the ORACLE_HOME/bin directory on the computer that has the ORACLE_HOME installation.

Regeneration of Data Shared Library and ZIP files

The OCI Instant Client Data Shared Library, libociei.so, can be regenerated by performing the following steps in an Administrator Installation of ORACLE_HOME:

mkdir -p $ORACLE_HOME/rdbms/install/instantclient/light
cd $ORACLE_HOME/rdbms/lib
make -f ins_rdbms.mk ilibociei

A new version of the libociei.so Data Shared Library based on the current files in the ORACLE_HOME is then placed in the ORACLE_HOME/rdbms/install/instantclient directory.

Note that the location of the regenerated Data Shared Library, libociei.so, is different from that of the original Data Shared Library, libociei.so, which is located in the ORACLE_HOME/instantclient directory.The preceding steps also generate Instant Client ZIP files for OCI, OCCI, JDBC, and SQL*Plus.

Regeneration of data shared library and ZIP files is not available on Microsoft Windows platforms.

Database Connection Names for OCI Instant Client

All Oracle Net naming methods that do not require the ORACLE_HOME or TNS_ADMIN environment variables to locate configuration files, such as tnsnames.ora or sqlnet.ora, work in the Instant Client mode. In particular, the connection string can be specified in the following formats:

• A Thin-style connection string of the form:

  host:port:service_name
  

  For example:

  url="jdbc:oracle:oci:@//example.com:5521:bjava21"
  

• A SQL connection URL string of the form:

  //host:[port][/service name]
  

  For example:

  url="jdbc:oracle:oci:@//example.com:5521/bjava21
  

• As an Oracle Net keyword-value pair. For example:

  url="jdbc:oracle:oci:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp) 
    (HOST=dlsun242) (PORT=5521))
    (CONNECT_DATA=(SERVICE_NAME=bjava21)))"
  

Naming methods that require TNS_ADMIN to locate configuration files continue to work if the TNS_ADMIN environment variable is set.

If the TNS_ADMIN environment variable is not set and TNSNAMES entries, such as inst1, are used, then the ORACLE_HOME environment variable must be set and the configuration files are expected to be in the $ORACLE_HOME/network/admin directory.

The empty connection string is not supported. However, an alternate way to use the empty connection string is to set the TWO_TASK environment variable on UNIX systems, or the LOCAL variable on Microsoft Windows, to either a tnsnames.ora entry or an Oracle Net keyword-value pair. If TWO_TASK or LOCAL is set to a tnsnames.ora entry, then the tnsnames.ora file must be loaded by the TNS_ADMIN or ORACLE_HOME setting.

Example

Consider that the listener.ora file on the database server contains the following information:

LISTENER = (ADDRESS_LIST=(ADDRESS=(PROTOCOL=tcp)(HOST=server6)(PORT=1573)))

SID_LIST_LISTENER = (SID_LIST=
                     (SID_DESC=(SID_NAME=rdbms3)
                     (GLOBAL_DBNAME=rdbms3.server6.us.alchemy.com)
                     (ORACLE_HOME=/home/dba/rdbms3/oracle)))

You can connect to this server in one of the following ways:

url = "jdbc:oracle:oci:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)
                     (HOST=server6)(PORT=1573))
                     (CONNECT_DATA=(SERVICE_NAME=rdbms3.server6.us.alchemy.com)))"

or:

url = "jdbc:oracle:oci:@//server6:1573/rdbms3.server6.us.alchemy.com"

Alternatively, you can set the TWO_TASK environment variable to any of the connection strings and connect to the database server without specifying the connection string along with the sqlplus command. For example, set the TWO_TASK environment in one of the following ways:

setenv TWO_TASK "(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=server6)(PORT=1573))
                 (CONNECT_DATA=(SERVICE_NAME=rdbms3.server6.us.alchemy.com)))"

or:

setenv TWO_TASK //server6:1573/rdbms3.server6.us.alchemy.com

Now, you can connect to the database server using the following URL:

url = "jdbc:oracle:oci:@"

The connection string can also be stored in the tnsnames.ora file. For example, consider that the tnsnames.ora file contains the following:

conn_str = (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=server6)(PORT=1573))
                (CONNECT_DATA=(SERVICE_NAME=rdbms3.server6.us.alchemy.com)))

If this tnsnames.ora file is located in the /home/webuser/instantclient directory, then you can set the TNS_ADMIN environment variable (or LOCAL on Microsoft Windows) as follows:

setenv TNS_ADMIN /home/webuser/instantclient

Now, you can connect as follows:

url = "jdbc:oracle:oci:@conn_str"

If this tnsnames.ora file is located in the /network/server6/home/dba/oracle/network/admin directory in the Oracle home, then instead of using TNS_ADMIN to locate the tnsnames.ora file, you can set the ORACLE_HOME environment variable as follows:

setenv ORACLE_HOME /network/server6/home/dba/oracle

Now, you can connect with either of the conn_str connection strings, as specified previously.

If tnsnames.ora can be located by TNS_ADMIN or ORACLE_HOME, then TWO_TASK can be set to:

setenv TWO_TASK conn_str

You can then connect with the following URL:

url = "jdbc:oracle:oci:@"

Environment Variables for OCI Instant Client

The ORACLE_HOME environment variable no longer determines the location of the NLS, CORE, and error message files. An OCI-only application does not require the ORACLE_HOME environment variable to be set. However, if the variable is set, then it does not have an impact on the operation of the OCI driver. OCI driver always obtains its data from the Data Shared Library. If the Data Shared Library is not available, only then the ORACLE_HOME environment variable is used and a full client installation is assumed. Even though the ORACLE_HOME environment variable is not required to be set, if it is set, then it must be set to a valid operating system path name that identifies a directory.

Environment variables ORA_NLS10 and ORA_NLSPROFILES33 are ignored in the Instant Client mode.

In the Instant Client mode, if the ORA_TZFILE variable is not set, then the larger, the default, timezlrg_n.dat file from the Data Shared Library is used. If the smaller timezone_n.dat file is to be used from the Data Shared Library, then set the ORA_TZFILE environment variable to the name of the file without any absolute or relative path names. That is:

On UNIX systems:

setenv ORA_TZFILE timezone_n.dat

On Microsoft Windows:

set ORA_TZFILE timezone_n.dat

In the examples above, n is the time zone data file version number.

If the OCI driver is not operating in the Instant Client mode because of nonavailability of the Data Shared Library, then the ORA_TZFILE variable, if set, names a complete path name, as it does in previous Oracle Database releases.

If TNSNAMES entries are used, then, as mentioned earlier, the TNS_ADMIN directory must contain the TNSNAMES configuration files, and if TNS_ADMIN is not set, then the ORACLE_HOME/network/admin directory must contain Oracle Net Services configuration files.

Globalization Settings

The NLS_LANG setting determines the language, territory, and character set as language_territory.characterset. In Instant Client Light, language can only be American, territory can be any that is supported, and characterset can be any one of the following:

• Single-byte

  • US7ASCII

  • WE8DEC

  • WE8MSWIN1252

  • WE8ISO8859P1

• Unicode

  • UTF8

  • AL16UTF16

  • AL32UTF8

Specifying character set or national character set other than those listed as the client or server character set or setting the language in NLS_LANG on the client will throw one of the following errors:

• ORA-12734

• ORA-12735

• ORA-12736

• ORA-12737

With Instant Client Light, the error messages obtained are only in English. Therefore, the valid values for the NLS_LANG setting are of the type:

American_territory.characterset

where, territory can be any valid and supported territory and characterset can be any one the previously listed character sets.

Instant Client Light can operate with the OCI environment handles created in the OCI_UTF16 mode.

Operation

To operate in the Instant Client Light mode, an application must set the LD_LIBARARY_PATH environment variable in UNIX systems or the PATH environment variable in Microsoft Windows to a location containing the client and data shared libraries. OCI applications by default look for the OCI Data Shared Library, libociei.so in the LD_LIBRARY_PATH environment variable in UNIX systems or the oraociei11.dll Data Shared Library in the PATH environment variable in Microsoft Windows, to determine if the application should operate in the Instant Client mode. In case this library is not found, then OCI tries to load the Instant Client Light Data Shared Library, libociicus.so in UNIX systems or libociicus11.dll in Microsoft Windows. If this library is found, then the application operates in the Instant Client Light mode. Otherwise, a non-Instant Client mode is assumed.

Installation

Instant Client Light can be installed in one of the following ways:

• From OTN

  You can download the required file from

  http://www.oracle.com/technology/tech/oci/instantclient/instantclient.html

  For Instant Client Light, instead of downloading and expanding the Basic package, download and unzip the Basic Light package. The instantclient_11_2 directory in which the lightweight libraries are unzipped should be empty before unzipping the files.

• From Client Admin Install

  Instead of copying libociei.so or oraociei11.dll from the ORACLE_HOME/instantclient directory, copy libociicus.so or oraociic10.dll from the ORACLE_HOME/instantclient/light directory. That is, the Instant Client directory on the LD_LIBRARY_PATH environment variable, in UNIX systems, should contain the Instant Client Light Data Shared Library, libociicus.so, instead of the larger OCI Instant Client Data Shared Library, libociei.so. In Microsoft Windows, the PATH environment variable should contain oraociicus11.dll instead of oraociei11.dll.

• From Oracle Universal Installer

  If the Instant Client option is selected from Oracle Universal Installer, then libociei.so (or oraociei11.dll on Microsoft Windows) is installed in the base directory of the installation which is going to be placed on the LD_LIBRARY_PATH environment variable. This is so that Instant Client Light is not enabled by default. The Instant Client Light Data Shared Library, libociicus.so (or oraociicus11.dll on Microsoft Windows), is installed in the light subdirectory of the base directory. Therefore, to operate in the Instant Client Light mode, the OCI Data Shared Library, libociei.so (or oraociei11.dll on Windows) must be deleted or renamed and the Instant Client Light Data Shared Library must be copied from the light subdirectory to the base directory of the installation.

  For example, if Oracle Universal Installer has installed the Instant Client in my_oraic_11_1 directory on the LD_LIBRARY_PATH environment variable, then one would need to do the following to operate in the Instant Client Light mode:

  cd my_oraic_11_1
  rm libociei.so
  mv light/libociicus.so .
  

  Note:

  All the Instant Client files should always be copied or installed in an empty directory. This is to ensure that no incompatible binaries exist in the installation.