Setting Oracle Environmental Variables

Oracle Database Tips by Donald Burleson

In order to accomplish an Oracle install successfully, certain environmental variables are required. The following table lists the variables that are frequently set when using and installing Oracle Software.

ENVIRONMENTAL VARIABLE	DESCRIPTION
$LD_ASSUME_KERNEL	This variable must be set in order to run many of the Oracle tools on Linux such as Universal Installer, dbca or netmgr.
$LD_LIBRARY_PATH	This variable allows many Oracle programs to find shared object library files.
$ORACLE_BASE	This variable is required to perform an install of Oracle software. It is used to indicate the base directory for all versions of Oracle software. Unless the administrator indicates otherwise, the oraInventory directory is located at $ORACLE_BASE/../oraInventory, and is the location in which Oracle catalogs its many installed components.
$ORACLE_HOME	Setting the $ORACLE_HOME is not necessary for a successful install. However, setting it will pre-determine the value displayed for a home directory which can then be edited. After Oracle software is installed, this variable helps Oracle find files. For example, to make a database connection, Oracle will look for the tnsnames.ora file in $ORACLE_HOME/network/admin, and $ORACLE_HOME is required to run many programs such as SQLPLUS and RMAN.
$ORACLE_SID	When this variable is set, the user does not need to type in a SID name in the connect string. For example, sqlplus system/password@my_db can be shortened to sqlplus system/password. Although it is possible to set $ORACLE_SID in the .bash_profile as a default, it is not necessary. It can be set on the fly with the racenv script.
$PATH	This variable is used by Linux to find executables. For example, in order to run sqlplus from a command prompt without typing in the entire path, you must include its directory path in this variable.

Table 4.4: Variables frequently set when using/installing Oracle

Setting Default Environmental Variables for the Oracle User

When a user logs into Linux, a few scripts are run to set things up. One such script is the .bash_profile script. Use the gedit ~oracle/.bash_profile command to open Oracle's login script. Edit it so that the lines shown in Figure 4.13 are appended to the text.

The export command is used to set an environmental variable. To refer to a variable that has been set in a script or a command, the variable must be preceded with a dollar sign. It is a common practice in BASHscripting to type variables in upper case letters. Remember, Linux is case sensitive, so $oracle_home is not the same variable as $ORACLE_HOME.

Using the suCommand from Oracle's Login

With the ~oracle/.bash_profile file in place, the environmental variables used by Oracle software will be in place. On occasion, the sucommand will be used to switch to the root user. Doing so will make the root login a child process of the Oracle login, and thus, the environmental variables will be inherited.

However, root's standard $PATH variable, the one root gets when root logs in directly, will not be there. Instead, root will get the Oracle user's $PATH variable, which is different. Thus, after using the sucommand to switch to root, commands such as chkconfig will need to include the full path: /sbin/chkconfig.

Oracle's Optimal Flexible Architecture

Optimal Flexible Architecture(OFA) is a directory structure created to assist the database administrator by keeping the many different files required to run Oracle software in predictable locations on disks.

Oracle touts many advantages to using OFA, but there are two advantages that are particularly important. First, implementing the OFA standard ensures that future administrators of the database will understand the file structure in place. This is a good reason to implement OFA using the exact directory names suggested by Oracle. Second, OFA makes adding new versions of Oracle software and switching between databases that use different versions of Oracle is possible and easy.

Figure 4.14 displays the OFAstructure for an installation with two versions of Oracle software installed and two working databases. The databases are named db9i and db10g, suggesting that each database is running on a different software version.

On a typical production database server, there would be many mount-points. The disk mounted at /u01 is used to store the software versions. The database data-files of the various databases would be stored on disks mounted at /u02, /u03 and higher.

Oracle made a change to OFAwith the release of Oracle 10g. Now, the $ORACLE_HOME for a 10g installation is kept in a sub-directory of 10.1.0. The sub-directory is called db_1. The reason for this change is that it allows for the install of the same product more than one time, such as creating a new 10g software install in the subdirectory db_2. It also allows for the install of a different Oracle product in a different sub-directory. For example, Oracle Client software could be installed in client_1.

To create the necessary directories for an Oracle 9i install, run the commands shown in Figure 4.15 on each node.

Important Oracle Files outside of the OFADirectory Structure

There is small number of files that Oracle places in locations outside of the OFA directory structure. After an install, the files listed in the following table will be shown.

PATH AND FILE	DESCRIPTION
/etc/oratab (9i) /var/opt/oracle/oratab (user created link only - 10g)	The oratab file is used to identify each SID with its associated ORACLE_HOME.
/var/opt/oracle/srvConfig.loc (9i) /etc/oracle/ocr.loc (10g)	This is a text file that identifies the location of the file used for cluster configuration and srvctl repository.
/etc/oraInst.loc (9i & 10g)	Identifies the location on disk of the Oracle inventory files and identifies the OS user group that owns the Oracle install. For a 10g install, this file is located in the $ORACLE_HOME directory.
/usr/local/bin/oraenv /usr/local/bin/racenv /usr/local/bin/coraenv /usr/local/bin/dbhome	These scripts are used to set environmental variables. The oraenv and racenv scripts are Bash shell scripts used extensively in this book. The coraenv script is used in the C shell. The dbhome script is used by the other three scripts to identify the home directory associated with given database.

Table 4.5: Files shown, after an install.

Installing the Oracle Patch 3006854

The code depot of this book includes the Oracle Patch 3006854. Refer to Appendix B for download instructions. The Oracle 9i software install will fail if this patch has not been installed on each node. To install the patch, follow the example in Figure 4.16. Ensure that the gcc program is available.

If the patch failed, most system commands such as ls will now return an error, a major problem! Figure 4.17 demonstrates the error and what can be done to fix this error. The patch must still be successfully run so that the /etc/libcwait.so and /etc/ld.so.preload files exist on the file system.

Learn More about PC RAC: