Install Oracle Database 21C and Create a Database on Oracle Linux 7

 This guide provides a practical, step-by-step procedure for installing Oracle Database 21c and creating a database on an Oracle Linux 7 x86_64 server.

The example uses the following directory structure:

/u01/app/oracle       Oracle software and database files
/u02                  Oracle installation software

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Step 0: Prerequisites

Before installing Oracle Database 21c, verify that the server meets the required prerequisites.

Server Requirements

Component	Requirement
Operating System	Oracle Linux 7.x x86_64
Memory	4 GB minimum; more recommended for production
Swap	15 GB or more
Disk	100 GB or more
Oracle Software	Oracle Database 19c for Linux x86_64

Check the server:

cat /etc/os-release
uname -r
free -h
df -h

Install Oracle Preinstallation Package

The Oracle preinstallation RPM automatically installs many required packages and configures the operating system for Oracle Database.

sudo yum install -y oracle-database-preinstall-21c

The package can configure:

• Required OS packages
• Oracle user and groups
• Kernel parameters
• Resource limits
• Other Oracle installation prerequisites

Verify the Oracle user:

id oracle

Example:

uid=54321(oracle) gid=54321(oinstall) groups=54321(oinstall),54322(dba)

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Step 1: Create Oracle User and Groups

If the preinstallation RPM was not used, create the Oracle groups and user manually.

sudo groupadd oinstall
sudo groupadd dba
sudo useradd -g oinstall -G dba oracle
sudo passwd oracle

The groups are used as follows:

• oinstall — Oracle software installation owner group
• dba — Database administrator group

Verify:

id oracle

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Step 2: Prepare Oracle Directories

Create the Oracle software and database directories.

sudo mkdir -p /u01/app/oracle
sudo mkdir -p /u01/app/oracle/oradata
sudo mkdir -p 

Set ownership and permissions:

sudo chown -R oracle:oinstall /u01
sudo chmod -R 775 /u01

Create a directory for the Oracle installation ZIP file:

sudo mkdir -p /u02
sudo chmod -R 775 /u02
sudo chown -R oracle:oinstall /u02

Directory Structure

/u01/app/oracle
├── product
│   └── 21c
│       └── dbhome_1
└── oradata

/u02
└── Oracle installation ZIP file

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Step 3: Configure Oracle Environment Variables

Switch to the Oracle user:

su - oracle

Edit the Oracle user's profile:

vi ~/.bash_profile

Add the following:

export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/21c/dbhome_1
export ORACLE_SID=PRODDB

export PATH=$ORACLE_HOME/bin:$PATH
export LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib
export CLASSPATH=$ORACLE_HOME/jlib:$ORACLE_HOME/rdbms/jlib

Apply the changes:

source ~/.bash_profile

Verify:

echo $ORACLE_BASE
echo $ORACLE_HOME
echo $ORACLE_SID

Expected:

/u01/app/oracle
/u01/app/oracle/product/21c/dbhome_1
PRODDB

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Step 4: Download Oracle Database 19c

Download the Oracle Database 21c Linux x86_64 software from the Oracle Software Downloads website.

Copy the ZIP file to:

/u02

For example:

cd /u02
ls -lrt 
chown oracle:oinstall V839960-01.zip

I forgot to create bellow directories create as bellow:---------
mkdir -p /u01/app/oracle/product/21c/dbhome_1
chown oracle:oinstall /u01/app/oracle/product/21c/dbhome_1

This is where you will install the Oracle Database 21c software.mkdir -p /u01/app/oraInventory
chown oracle:oinstall /u01/app/oraInventory
chmod 770 /u01/app/oraInventoryThis is Oracle's central inventory directorymkdir -p  /u01/app/oracle/FRA 
chown oracle:oinstall  /u01/app/oracle/FRA

FRA is used by Oracle for recovery-related files. 

Extract the Oracle software directly into the Oracle Home directory:

unzip /u02/V1011496-01.zip -d "$ORACLE_HOME"

Verify:

ls -l $ORACLE_HOME

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Step 5: Install Oracle Database Software

Oracle 21c Silent Install

Start the run installer in silent mode to begin the installation

cd $ORACLE_HOME/ ls -lrt you will see runInstaller

./runInstaller -ignorePrereqFailure -silent -waitForCompletion \
oracle.install.option=INSTALL_DB_SWONLY \
ORACLE_HOSTNAME=${HOSTNAME} \
UNIX_GROUP_NAME=oinstall \
INVENTORY_LOCATION=/u01/app/oraInventory \
SELECTED_LANGUAGES=en,en_GB \
ORACLE_HOME=${ORACLE_HOME} \
ORACLE_BASE=${ORACLE_BASE} \
oracle.install.db.InstallEdition=EE \
oracle.install.db.OSDBA_GROUP=dba \
oracle.install.db.OSOPER_GROUP=dba \
oracle.install.db.OSBACKUPDBA_GROUP=dba \
oracle.install.db.OSDGDBA_GROUP=dba \
oracle.install.db.OSKMDBA_GROUP=dba \
oracle.install.db.OSRACDBA_GROUP=dba \
SECURITY_UPDATES_VIA_MYORACLESUPPORT=false \
DECLINE_SECURITY_UPDATES=true \
oracle.installer.autoupdates.option=SKIP_UPDATES

Once installation is completed, run the root scripts and you can move to DBCA create database.
Step 08 : Create Database using DBCA silent mode

dbca -silent -createDatabase \

-templateName General_Purpose.dbc \

-gdbName prod \

-sid prod \

-createAsContainerDatabase true \

-numberOfPDBs 1 \

-pdbName prodpdb \

-emConfiguration NONE \

-datafileDestination /u01/app/oradata \

-storageType FS \

-characterSet AL32UTF8 \

-totalMemory 1500 \

-recoveryAreaDestination /u01/app/oracle/FRA

Enter SYS user password:  EnterCDB#123

Enter SYSTEM user password:  EnterCDB#123

keep both same

Verify

[oracle@prm ~]$ cat /etc/oratab | grep -i prod

ps -ef | grep pmon

su - oracle
 . oraenv
prod
sqlplus / as sysdba

SQL> select name,open_mode,cdb from v$database;

NAME      OPEN_MODE            CDB
--------- -------------------- ---
prod   READ WRITE           NO <------ NON-CDB

SQL> show con_name

CON_NAME
------------------------------
prod
SQL> archive log list

lets enable archiving.
shutdown immediate;
startup mount;
alter database archivelog;
alter database open;
archive log list;
alter system set db_recovery_file_dest_size=20G scope=both;
alter system set db_recovery_file_dest='/u01/app/oracle/FRA' scope=both;

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Step 7: Post-Installation Validation

force service registration:

tells the Oracle instance to immediately register its database services with the listener.

alter system register;

lsnrctl start
if you see The listener supports no services
do this 
show pdbs;
alter pluggable database PRODPDB open;
alter pluggable database PRODPDB save state;
alter system register;
lsnrctl start
lsnrctl status

Start the Database

Connect as SYSDBA:

sqlplus / as sysdba

Start the database:

STARTUP;

Check the database:

SELECT name, open_mode FROM v$database;

show pdbs

ALTER PLUGGABLE DATABASE PRODPDB OPEN;
 if you want PRODPDB to automatically open after a database restart:
ALTER PLUGGABLE DATABASE PRODPDB SAVE STATE;

Exit:

EXIT;

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Check the Listener

Run:

lsnrctl status

If the listener is not running:

force service registration:

tells the Oracle instance to immediately register its database services with the listener.

alter system register;

lsnrctl start

Verify again:

lsnrctl status

The default Oracle listener port is:

1521

Step 8: Test Database Connectivity

Test a local connection:

lest connect to pluggable database:

 sqlplus system@//prod.entopdba.com:1521/prodpdb

Enter the password when prompted.

For production environments, prompting for the password is preferable to placing it directly in shell history or scripts.

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Unlock the HR Schema

The HR sample schema is commonly used for Oracle training and laboratory exercises.

Step 1: Connect as SYSDBA

sqlplus / as sysdba

Step 2: Check the HR Account

SELECT username, account_status
FROM dba_users
WHERE username = 'HR';

Example:

USERNAME   ACCOUNT_STATUS
---------  -------------
HR         LOCKED

That's expected. Oracle Database 21c does not automatically create the classic HR sample schema when you create a database with DBCA.

Download the official sample schemas

As oracle:

cd /u01/app/oracle
wget -O db-sample-schemas.zip https://github.com/oracle/db-sample-schemas/archive/refs/heads/main.zip
unzip -q db-sample-schemas.zip

The official Oracle sample-schema repository contains the HR installation scripts.

Check:

find /u01/app/oracle -name hr_install.sql -o -name hr_main.sql

You should see something like:

/u01/app/oracle/db-sample-schemas-main/human_resources/hr_install.sql

2. Make sure PRODPDB is open

sqlplus / as sysdba

show pdbs;

alter pluggable database PRODPDB open;

alter pluggable database PRODPDB save state;

Then explicitly switch into the PDB:

alter session set container=PRODPDB;

show con_name;

You want:

CON_NAME
------------------------------
PRODPDB

3. Install HR

I recommend using the 21c hr_install.sql script from the current Oracle sample-schema repository. Oracle's 21c documentation specifically describes hr_install.sql as the HR installation script, and it creates the HR user, objects, and sample data.

Exit SQL*Plus:

exit

Then:

cd /u01/app/oracle/db-sample-schemas-main/human_resources

Start SQL*Plus against PRODPDB, not the CDB root:

sqlplus system@//prod.entopdba.com:1521/prodpdb

Enter your SYSTEM password.

Then:

@hr_install.sql

It will ask for the HR password and tablespace. Use:

HR password:        <choose a password>
Default tablespace: USERS

Lets connect to HR Schema,

sqlplus hr@//prod.entopdba.com:1521/prodpdb

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Final Verification Checklist

Before considering the installation complete, verify:

✓ Oracle Linux configured
✓ Required packages installed
✓ oracle user created
✓ oinstall and dba groups configured
✓ /u01 and /u02 created
✓ ORACLE_BASE configured
✓ ORACLE_HOME configured
✓ Oracle 21c software installed
✓ Root scripts completed
✓ Database created with DBCA
✓ Listener running on port 1521
✓ Database OPEN
✓ Client connection tested
✓ HR schema tested (optional)

Installation Flow

Linux Server
     ↓
OS Prerequisites
     ↓
Oracle Preinstall RPM
     ↓
Oracle User & Groups
     ↓
/u01 and /u02
     ↓
Environment Variables
     ↓
Oracle 21c Software
     ↓
Listener
     ↓
DBCA
     ↓
PRODDB Database
     ↓
Validation & Testing

Conclusion: Following these steps provides a basic Oracle Database 21c installation suitable for a lab, development environment, or as a starting point for a production deployment. Production systems should additionally be configured for backup/recovery, monitoring, security, patching, storage performance, and high availability according to the organization's requirements.