Installing oracle XE in CentOS 6

In this article I'll describe how we can install oracle 11g express edition in CentOS 6. The download is a zip file oracle-xe-11.2.0-1.0.x86_64.rpm.zip.

We get started by extracting the zip file and installing the rpm.

[root@walk XE]# ls
oracle-xe-11.2.0-1.0.x86_64.rpm.zip
[root@walk XE]# unzip oracle-xe-11.2.0-1.0.x86_64.rpm.zip
Archive:  oracle-xe-11.2.0-1.0.x86_64.rpm.zip
   creating: Disk1/
   creating: Disk1/upgrade/
  inflating: Disk1/upgrade/gen_inst.sql
   creating: Disk1/response/
  inflating: Disk1/response/xe.rsp
  inflating: Disk1/oracle-xe-11.2.0-1.0.x86_64.rpm
[root@walk XE]#

[root@walk Disk1]# rpm -ivh oracle-xe-11.2.0-1.0.x86_64.rpm
Preparing...                ########################################### [100%]
   1:oracle-xe              ########################################### [100%]
Executing post-install steps...
You must run '/etc/init.d/oracle-xe configure' as the root user to configure the database.

Next, as directed we proceed to launch the database configuration wizard.

[root@walk ~]# /etc/init.d/oracle-xe configure

Oracle Database 11g Express Edition Configuration
-------------------------------------------------
This will configure on-boot properties of Oracle Database 11g Express
Edition.  The following questions will determine whether the database should
be starting upon system boot, the ports it will use, and the passwords that
will be used for database accounts.  Press <Enter> to accept the defaults.
Ctrl-C will abort.

Specify the HTTP port that will be used for Oracle Application Express [8080]:

Specify a port that will be used for the database listener [1521]:

Specify a password to be used for database accounts.  Note that the same
password will be used for SYS and SYSTEM.  Oracle recommends the use of
different passwords for each database account.  This can be done after
initial configuration:
Confirm the password:

Do you want Oracle Database 11g Express Edition to be started on boot (y/n) [y]:y

Starting Oracle Net Listener...Done
Configuring database...Done
Starting Oracle Database 11g Express Edition instance...Done
Installation completed successfully.


This takes care of creating the required oracle user and dba group along with creating and populating the /u01 directory with all the content that the DB will need.

This also installs oracle-xe script in /etc/init.d to control the database through init.

[root@walk ~]# ls -l /etc/init.d/oracle-xe
-rwxr-xr-x. 1 root root 19592 Aug 29  2011 /etc/init.d/oracle-xe

We can treat the DB instance as a service and view it's status like any other init service:

[root@walk ~]# /etc/init.d/oracle-xe status

LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 07-OCT-2017 11:18:15

Copyright (c) 1991, 2011, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC_FOR_XE)))

STATUS of the LISTENER

------------------------

Alias                     LISTENER

Version                   TNSLSNR for Linux: Version 11.2.0.2.0 - Production

Start Date                07-OCT-2017 10:18:59

Uptime                    0 days 0 hr. 59 min. 16 sec

Trace Level               off

Security                  ON: Local OS Authentication

SNMP                      OFF

Default Service           XE

Listener Parameter File   /u01/app/oracle/product/11.2.0/xe/network/admin/listener.ora

Listener Log File         /u01/app/oracle/diag/tnslsnr/walk/listener/alert/log.xml

Listening Endpoints Summary...

  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC_FOR_XE)))

  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=walk)(PORT=1521)))

Services Summary...

Service "PLSExtProc" has 1 instance(s).

  Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...

Service "XE" has 1 instance(s).

  Instance "XE", status READY, has 1 handler(s) for this service...

Service "XEXDB" has 1 instance(s).

  Instance "XE", status READY, has 1 handler(s) for this service...

The command completed successfully

Now we will switch to the oracle user, set up our environment and connect to the database via SQLplus.

-bash-4.1$ id -a oracle

uid=500(oracle) gid=500(dba) groups=500(dba)

-bash-4.1$ cat /u01/app/oracle/product/11.2.0/xe/bin/oracle_env.sh

export ORACLE_HOME=/u01/app/oracle/product/11.2.0/xe

export ORACLE_SID=XE

export NLS_LANG=`$ORACLE_HOME/bin/nls_lang.sh`

export PATH=$ORACLE_HOME/bin:$PATH

-bash-4.1$ . /u01/app/oracle/product/11.2.0/xe/bin/oracle_env.sh

As shown the environment variables are available in the script oracle_env.sh and we need to source it for the variables to come into effect. To avoid running the script at each login we could just add these variables to the .bash_profile file for the oracle user.

Now let's launch SQLplus.

-bash-4.1$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.2.0 Production on Sat Oct 7 10:27:42 2017

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected to:

Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production

SQL>

Connecting to the instance via "/ as sysdba" is like connecting as root user in Linux. This denotes full administrative access over the instance.

Let's query the v$instance and v$database views to take a look at the instance status:

SQL> SELECT INSTANCE_NAME, STATUS, DATABASE_STATUS FROM V$INSTANCE;

INSTANCE_NAME    STATUS       DATABASE_STATUS

---------------- ------------ -----------------

XE               OPEN         ACTIVE

SQL> SELECT NAME,CREATED,LOG_MODE,OPEN_MODE FROM V$DATABASE;

NAME      CREATED            LOG_MODE     OPEN_MODE

--------- ------------------ ------------ --------------------

XE        07-OCT-17          NOARCHIVELOG READ WRITE

From a system admin's perspective we tend to look for the pmon process to confirm if a DB is running or not.

[root@walk ~]# ps -ef | grep oracle | grep pmon

oracle     4853      1  0 10:22 ?        00:00:00 xe_pmon_XE