Switch to the oracle user and set ORACLE_SID, ORACLE_HOME, and PATH environment variables. 2. Use sqlplus / as sysdba to access SQLPlus, then run SHUTDOWN IMMEDIATE to stop the database or STARTUP to start it, which initializes the instance, mounts the database, and opens it for users. 3. Optionally, manage the listener separately using lsnrctl start or lsnrctl stop to enable or disable remote connections. 4. For automation, use custom scripts or systemd services if configured, though manual SQLPlus control remains the standard method. Always verify correct ORACLE_SID and ORACLE_HOME settings, especially when multiple databases exist on the same server.

Starting and stopping an Oracle database on Linux involves using Oracle’s command-line tools, primarily through the sqlplus utility and sometimes via Oracle’s dbca or service scripts depending on the setup. Below are the standard methods for manually starting and stopping an Oracle database instance.

1. Switch to the Oracle User and Set Environment Variables

Before managing the database, you need to log in or switch to the Oracle software owner (usually oracle) and ensure the Oracle environment is set.

sudo su - oracle

Make sure ORACLE_SID and ORACLE_HOME are set. You can set them manually if needed:

export ORACLE_SID=orcl
export ORACLE_HOME=/u01/app/oracle/product/19.0.0/dbhome_1
export PATH=$ORACLE_HOME/bin:$PATH

Replace orcl and the ORACLE_HOME path with your actual database SID and Oracle installation path.

*2. Use SQLPlus to Start and Stop the Database**

Stop the Oracle Database

Connect to the database as SYSDBA and shut it down:

sqlplus / as sysdba

Once in SQL*Plus:

SHUTDOWN IMMEDIATE;

• SHUTDOWN IMMEDIATE rolls back uncommitted transactions and disconnects users. It's the most common safe shutdown method.
• Other options: SHUTDOWN TRANSACTIONAL, SHUTDOWN NORMAL (graceful), or SHUTDOWN ABORT (like a crash – only if necessary).

After shutdown, you can exit:

EXIT;

Start the Oracle Database

Restart the instance and mount and open the database:

sqlplus / as sysdba

Then:

STARTUP;

This command does the following:

• Starts an instance (allocates memory and starts background processes)
• Mounts the database (associates the instance with the database)
• Opens the database (makes it available to users)

If you only want to mount or open partially, you can use:

• STARTUP NOMOUNT – instance started, no database mounted (used for creating databases or recovery)
• STARTUP MOUNT – instance and database mounted, but not open (used for maintenance)
• STARTUP OPEN – fully opens the database (default with STARTUP)

3. Optional: Using Oracle Net and Listener Control

The database listener (usually LISTENER) runs separately and should also be managed:

Stop the Listener

lsnrctl stop

Start the Listener

lsnrctl start

The listener allows remote clients to connect. Always ensure it's running after starting the database.

4. Automating with Scripts (Optional)

On some systems, especially with Oracle Restart or systemd (in newer setups), you can use scripts or services.

For example, using a custom systemd service is possible but not standard unless configured. Most Oracle DBAs prefer manual sqlplus control or Oracle Grid Infrastructure.

Quick Summary Commands

As the oracle user:

# Stop the database
sqlplus / as sysdba << EOF
SHUTDOWN IMMEDIATE;
EXIT;
EOF

# Start the database
sqlplus / as sysdba << EOF
STARTUP;
EXIT;
EOF

# Listener control
lsnrctl start    # or stop

Note: Always ensure you're using the correct ORACLE_SID and ORACLE_HOME. Multiple databases on the same server require switching these variables accordingly.

Basically, it's sqlplus / as sysdba followed by STARTUP or SHUTDOWN IMMEDIATE. Not complex, but easy to mess up if environment variables are wrong.

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