ORACLE DBA CHRONICLES: Linux Commands

Using Linux commands is crucial for Oracle DBAs to manage databases effectively. Here's a guide to essential Linux commands for Oracle DBA beginners, categorized based on their usage:-

1. Basic Linux Commands:-

These commands help navigate and interact with the Linux environment

Check the current directory:-

pwd

List files in a directory:-

ls -l

Change directory:-

cd /path/to/directory

View file content:-

cat filename

Edit files (e.g., configuration files):-

vi filename

Copy files:-

cp source_file target_file

Move or rename files:-

mv source_file target_file

Delete files:-

rm filename

Check disk space usage:

df -h

Check memory usage

free -h

2. User and Permission Management

Oracle software often requires specific users and permissions.

Switch to Oracle user:

su - oracle

Check current user:

whoami

Change file permissions:

chmod 755 filename

Change file owner to oracle:

chown oracle:oinstall filename

3. Oracle Environment Setup:-

Before running Oracle commands, set environment variables.

Set ORACLE_HOME:

export ORACLE_HOME=/u01/app/oracle/product/19c/dbhome_1

Set ORACLE_SID:

export ORACLE_SID=orcl

Update PATH:

export PATH=$ORACLE_HOME/bin:$PATH

Verify environment variables:

env | grep ORACLE

4. Managing Oracle Database

Basic commands for starting, stopping, and checking the database.

Check listener status:

lsnrctl status

Start listener:

lsnrctl start

Stop listener:

lsnrctl stop

sqlplus / as sysdba

Start the database:

startup;

Shut down the database:

shutdown immediate;

5. Monitoring Logs

Log files are critical for troubleshooting Oracle issues.

Navigate to log directory:

cd $ORACLE_HOME/diag/rdbms/orcl/orcl/trace

View alert log file:

tail -f alert_orcl.log

6. Backup and Restore Commands

Database backups often involve file management.

Copy database files:

cp /path/to/source /path/to/backup

Compress files:

tar -czvf backup.tar.gz /path/to/backup

Uncompressed files:

tar -xzvf backup.tar.gz

7. Performance Monitoring

Monitor system performance to ensure optimal database operation.

Check CPU usage:

top

Check running processes:

ps -ef | grep oracle

Check open ports:

netstat -tuln | grep 1521

8. Scheduling Jobs

Automate tasks using cron jobs.

Edit crontab:

crontab -e

Example cron job to run a backup script daily at midnight:

0 0 * * * /path/to/backup_script.sh

9. Secure Database Access

Manage database security with file and process restrictions.

Restrict file access:

chmod 600 filename

Monitor unauthorized access:

last

10. Debugging and Troubleshooting

Identify and resolve common issues.

Check system logs:

tail -f /var/log/messages

Identify memory leaks:

vmstat 1

Check Oracle process details:

ps -ef | grep pmon

ORACLE DBA CHRONICLES