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Friday, 5 June 2026

SSH Equivalency Setup in Oracle Exadata – Step-by-Step Guide

Introduction

SSH equivalency is a mandatory requirement in Oracle Exadata environments. It enables passwordless SSH communication between database servers, storage servers (cells), and other Exadata components.

SSH equivalency is used during:

Exadata deployment
OneCommand setup
Patching activities
Exachk execution
Automation scripts
Cluster operations

This guide demonstrates how to configure SSH equivalency securely in an Oracle Exadata environment.

Environment Details

Example Exadata Environment:

Hostname	Type
db01	Database Server
db02	Database Server
cell01	Storage Server
cell02	Storage Server
cell03	Storage Server

User:

oracle

Step 1: Verify Connectivity

From db01, verify connectivity to all nodes.

ping db02
ping cell01
ping cell02
ping cell03

Expected Result:

64 bytes from db02
64 bytes from cell01

Step 2: Generate SSH Key

su - oracle

Generate SSH key.

ssh-keygen -t rsa

Press Enter for all prompts.

Verify key files:

ls -ltr ~/.ssh

Expected:

id_rsa
id_rsa.pub

Step 3: Copy Public Key to Remote Servers

Copy public key to all target nodes.

ssh-copy-id oracle@db02

ssh-copy-id oracle@cell01

ssh-copy-id oracle@cell02

ssh-copy-id oracle@cell03

Enter password when prompted.

Step 4: Verify Passwordless Login

Test SSH connectivity.

ssh db02 hostname

ssh cell01 hostname

ssh cell02 hostname

ssh cell03 hostname

Expected Output:

db02
cell01
cell02
cell03

No password should be requested.

Step 5: Configure Reverse Connectivity

Perform the same steps from db02 to db01.

Generate keys:

ssh-keygen -t rsa

Copy keys:

ssh-copy-id oracle@db01

Validate:

ssh db01 hostname

Step 6: Validate SSH Equivalency

Execute the following command from each database node.

ssh db01 date

ssh db02 date

ssh cell01 date

ssh cell02 date

ssh cell03 date

All commands should execute without password prompts.

Step 7: Verify Authorized Keys

Check authorized_keys file.

cat ~/.ssh/authorized_keys

Ensure public keys from all participating nodes are present.

Permissions:

chmod 700 ~/.ssh

chmod 600 ~/.ssh/authorized_keys

chmod 600 ~/.ssh/id_rsa

Common Issues and Troubleshooting

Permission Denied

Error:

Permission denied (publickey)

Solution:

chmod 700 ~/.ssh

chmod 600 ~/.ssh/authorized_keys

Host Key Verification Failed

Error:

Host key verification failed

Solution:

ssh-keygen -R hostname

Reconnect:

ssh hostname

SSH Timeout

Verify:

ping hostname

nslookup hostname

Check firewall configuration.

Validation Checklist

Check	Status
SSH keys generated	✓
Public keys copied	✓
Passwordless login working	✓
Authorized keys validated	✓
Permissions verified	✓

Conclusion

SSH equivalency is a critical prerequisite for Oracle Exadata administration, patching, and automation activities. Properly configured passwordless SSH improves operational efficiency and reduces manual intervention during maintenance and deployment tasks.

Always validate connectivity and file permissions after configuration to avoid failures during patching and cluster operations.

Saturday, 18 October 2025

Steps to Create and Connect to Azure Database for PostgreSQL

Steps to Create and Connect to Azure Database for PostgreSQL

Create PostgreSQL Database in Azure Portal

Go to the Azure Portal.
Search for and select Azure Database for PostgreSQL servers.
Click Create, then select Flexible Server option.

Get Connection Information

In the newly created server’s Overview page, copy the Server name and Username; you will need these to connect.

Connect Using pgAdmin

Open pgAdmin.
Right-click Servers and select Create > Server.
Enter a name, e.g., azure-pg-tt.
On the Connection tab, enter the copied hostname and username from the Azure Portal.
Click Save to connect.

Explore Created Databases

Expand the connected server in pgAdmin. You will see 3 databases pre-created by Azure. Do not delete these.

Create a New Database to Use

Right-click Databases under your server, select Create > Database.
Name your new database, for example, mypgsqldb.

Run SQL Queries on Your Database

Select your new database (mypgsqldb) and click the Query Tool icon in pgAdmin.
Run the following SQL commands to create a table, insert records, and query data:

sql

CREATE TABLE EMP(id serial PRIMARY KEY, name VARCHAR(50), Salary INTEGER);

INSERT INTO EMP(id, name, salary) VALUES (1, 'Jon', 15000);

INSERT INTO EMP(id, name, salary) VALUES (2, 'Doe', 15400);

SELECT * FROM EMP;

You are now connected to the PostgreSQL database on Azure !!!!!!

Create a Free SQL Database in Azure and query using query editor

How to Create a Free SQL Database in Azure (with Screenshots)

Getting started with SQL databases in the cloud is easy with Microsoft Azure. Follow the step-by-step tutorial below to create your own free Azure SQL Database and run queries using the Azure Portal.

1. Log in to the Azure Portal

Go to https://portal.azure.com/ and sign in with your Microsoft account. On the homepage, you’ll find options like Create a resource, Azure SQL Database, and more.

2. Create a New SQL Database

Click on Azure SQL Database or use the search bar to find it. Click the Create button to start the creation process.

3. Configure Database Basics

Fill out the basic details:

Subscription: Choose your Azure subscription.
Resource group: Create a new resource group or select an existing one.
Database name: Enter a meaningful name.
Server: Click "Create new" to set up a SQL server (see next step).

4. Set Up SQL Database Server

In the server creation form, provide:

Server name: A unique name.
Location: Select the Azure region.
Authentication: Set admin login and password.

5. Configure Networking Options

On the networking screen:

Set Allow Azure services and resources to access this server to No.
Set Add current client IP address to Yes.

6. Additional Settings: Add Sample Data

On the Additional settings tab, choose Sample under “Use existing data”. This loads the AdventureWorksLT sample database for learning and testing.

7. Review and Create

Click Review + create at the bottom and let Azure deploy your database.

8. Query the Database

Once deployed, go back to the list of your SQL databases and select the one you’ve just created.2_Create.jpg

Open Query editor (preview).
Log in with the credentials you set for your server.

9. Sample Query and Output

Here’s how the query and results look in the Azure Portal’s Query Editor :

sql

SELECT * FROM [SalesLT].[Customer]

You’ll see a result table with columns such as CustomerID, NameStyle, Title, and FirstName.

Sunday, 21 September 2025

Oracle database To Configure Data Guard Physical Standby is on the way .........................................

New post

DGMGRL> show configuration;

Configuration - PRIMARY_ORADB

Protection Mode: MaxPerformance

Members:

oradb - Primary database

oradbsby - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:

SUCCESS (status updated 13 seconds ago)

ORA-01102: cannot mount database in EXCLUSIVE mode

The ORA-01102 error "cannot mount database in EXCLUSIVE mode" occurs when an Oracle instance tries to mount the database in exclusive mode but another instance has already mounted the database either exclusively or in parallel mode.

1. Shutdown any other instances that may have the database mounted:

SHUTDOWN IMMEDIATE;

2. Kill any remaining Oracle background or shadow processes related to the database using OS commands:

kill -9 <process_ids>

[oracle@muthu ~]$ ps -ef|grep pmon

oracle 1821 1 0 16:40 ? 00:00:00 ora_pmon_oradbsby

oracle 2750 1 0 16:41 ? 00:00:00 ora_pmon_oradb

oracle 2936 2626 0 16:42 pts/0 00:00:00 grep --color=auto pmon

[oracle@muthu ~]$ kill -9 2750

[oracle@muthu ~]$ kill -9 1821

3. Check and remove the stale lock file lk<SID> in the $ORACLE_HOME/dbs directory if it exists.

4. Remove any leftover shared memory segments and semaphores related to the Oracle SID.

5. In RAC, verify the cluster_database parameter is set to TRUE for all instances.

6. After cleaning up, start the database again:

STARTUP MOUNT;

This error is mostly about ensuring no conflicting instance is holding the database open and cleaning up orphaned processes or locks so the instance can mount the database exclusively without conflict.

Saturday, 20 September 2025

To recover the lost logs in oracle database

***

Oracle Database Recovery and Backup Task Documentation

This document describes the steps performed for deleting redo log files, performing an RMAN point-in-time recovery, and backing up the database with archived logs in an Oracle 12c environment with a multitenant container database (CDB) and pluggable database (PDB).

***

Environment and Initial Setup

- Oracle Database version: 12c Release 12.2.0.1.0 (64-bit Enterprise Edition)

- Working with Container Database (CDB) and Pluggable Database (PDB1)

- OS user: oracle

- Date and time of operations: Sep 20, 2025, around 18:30 to 18:50 +04 timezone

***

Step 1: Switch Container and Create Table

1. Set container to PDB1:

SQL> alter session set container=PDB1;

Session altered.

2. Verify PDB status:SQL> show pdbs

CON_ID CON_NAME OPEN MODE RESTRICTED

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

3 PDB1 READ WRITE NO

3. Create a simple table named `emp` with columns `id` (int) and `name` (varchar(100)):

SQL> create table emp(id int,name varchar(100));

Table created.

4. Insert one row into the `emp` table:

SQL> insert into emp values (1,'Muthu');

1 row created.

SQL> commit;

Commit complete.

5. Validate the data insertion:

SQL> select * from emp;

ID NAME

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

1 Muthu

6. Check the current System Change Number (SCN):

SQL> select current_scn from v$database;

CURRENT_SCN

-----------

2779187

7. Confirm the current date/time from the OS shell:

SQL> !date

Sat Sep 20 18:32:15 +04 2025

***

Step 2: List and Remove Redo Log Files

1. List redo log members (files):

SQL> select member from v$logfile;

MEMBER

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

/u01/app/oracle/oradata/oradb/redo03.log

/u01/app/oracle/oradata/oradb/redo02.log

/u01/app/oracle/oradata/oradb/redo01.log

2. List the contents of Oracle data directory:

SQL> !ls -lrt /u01/app/oracle/oradata/oradb/

total 2498756

drwxr-x---. 2 oracle oinstall 4096 Sep 4 2020 pdbseed

drwxr-x---. 2 oracle oinstall 104 Sep 4 2020 pdb1

-rw-r-----. 1 oracle oinstall 142614528 Sep 20 18:20 temp01.dbf

-rw-r-----. 1 oracle oinstall 209715712 Sep 20 18:36 redo01.log

-rw-r-----. 1 oracle oinstall 209715712 Sep 20 18:37 redo02.log

-rw-r-----. 1 oracle oinstall 849354752 Sep 20 18:37 system01.dbf

-rw-r-----. 1 oracle oinstall 639639552 Sep 20 18:37 sysaux01.dbf

-rw-r-----. 1 oracle oinstall 283123712 Sep 20 18:37 undotbs01.dbf

-rw-r-----. 1 oracle oinstall 5251072 Sep 20 18:37 users01.dbf

-rw-r----- 1 oracle oinstall 209715712 Sep 20 18:37 redo03.log

-rw-r-----. 1 oracle oinstall 18726912 Sep 20 18:38 control01.ctl

3. Remove all redo log files from directory:

SQL> !rm /u01/app/oracle/oradata/oradb/redo*

4. Confirm redo log files removal by listing directory again:

SQL> !ls -lrt /u01/app/oracle/oradata/oradb/

total 1884344

drwxr-x---. 2 oracle oinstall 4096 Sep 4 2020 pdbseed

drwxr-x---. 2 oracle oinstall 104 Sep 4 2020 pdb1

-rw-r-----. 1 oracle oinstall 142614528 Sep 20 18:20 temp01.dbf

-rw-r-----. 1 oracle oinstall 849354752 Sep 20 18:37 system01.dbf

-rw-r-----. 1 oracle oinstall 639639552 Sep 20 18:37 sysaux01.dbf

-rw-r-----. 1 oracle oinstall 283123712 Sep 20 18:37 undotbs01.dbf

-rw-r-----. 1 oracle oinstall 5251072 Sep 20 18:37 users01.dbf

-rw-r-----. 1 oracle oinstall 18726912 Sep 20 18:38 control01.ctl

***

Step 3: Shutdown Database and Mount for Recovery

1. Shutdown the database immediately:

SQL> shut immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup mount;

ORACLE instance started.

Total System Global Area 801112064 bytes

Fixed Size 8797872 bytes

Variable Size 423625040 bytes

Database Buffers 360710144 bytes

Redo Buffers 7979008 bytes

Database mounted.

SQL> exit

Disconnected from Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

***

Step 4: RMAN Point-in-Time Recovery to a Specific Sequence

1. Start RMAN and connect to target database:

[oracle@muthu trace]$ rman target /

Recovery Manager: Release 12.2.0.1.0 - Production on Sat Sep 20 18:40:06 2025

connected to target database: ORADB (DBID=2803495960, not open)

2. Run recovery commands:

RMAN> run

{

set until sequence 3;

restore database;

recover database;

alter database open resetlogs;

}2> 3> 4> 5> 6> 7>

executing command: SET until clause

Starting restore at 20-SEP-2025 18:40:21

using target database control file instead of recovery catalog

flashing back control file to SCN 2780743

allocated channel: ORA_DISK_1

channel ORA_DISK_1: SID=20 device type=DISK

skipping datafile 5; already restored to file /u01/app/oracle/oradata/oradb/pdbseed/system01.dbf

skipping datafile 6; already restored to file /u01/app/oracle/oradata/oradb/pdbseed/sysaux01.dbf

skipping datafile 8; already restored to file /u01/app/oracle/oradata/oradb/pdbseed/undotbs01.dbf

channel ORA_DISK_1: starting datafile backup set restore

channel ORA_DISK_1: specifying datafile(s) to restore from backup set

channel ORA_DISK_1: restoring datafile 00001 to /u01/app/oracle/oradata/oradb/system01.dbf

channel ORA_DISK_1: restoring datafile 00003 to /u01/app/oracle/oradata/oradb/sysaux01.dbf

channel ORA_DISK_1: restoring datafile 00004 to /u01/app/oracle/oradata/oradb/undotbs01.dbf

channel ORA_DISK_1: restoring datafile 00007 to /u01/app/oracle/oradata/oradb/users01.dbf

channel ORA_DISK_1: reading from backup piece /u01/app/oracle/fra/oradb/ORADB/backupset/2025_09_20/o1_mf_nnndf_TAG20250920T183632_ndxgzjpn_.bkp

channel ORA_DISK_1: piece handle=/u01/app/oracle/fra/oradb/ORADB/backupset/2025_09_20/o1_mf_nnndf_TAG20250920T183632_ndxgzjpn_.bkp tag=TAG20250920T183632

starting media recovery

archived log for thread 1 with sequence 1 is already on disk as file /u01/app/oracle/fra/oradb/ORADB/archivelog/2025_09_20/o1_mf_1_1_ndxgz7r8_.arc

archived log for thread 1 with sequence 2 is already on disk as file /u01/app/oracle/fra/oradb/ORADB/archivelog/2025_09_20/o1_mf_1_2_ndxh0h3t_.arc

archived log file name=/u01/app/oracle/fra/oradb/ORADB/archivelog/2025_09_20/o1_mf_1_1_ndxgz7r8_.arc thread=1 sequence=1

archived log file name=/u01/app/oracle/fra/oradb/ORADB/archivelog/2025_09_20/o1_mf_1_2_ndxh0h3t_.arc thread=1 sequence=2

media recovery complete, elapsed time: 00:00:01

Finished recover at 20-SEP-2025 18:40:53

Statement processed

RMAN>

***

Step 5: Validate Recovery and Backup

[oracle@muthu trace]$ sqlplus / as sysdba

SQL*Plus: Release 12.2.0.1.0 Production on Sat Sep 20 18:44:09 2025

Connected to:

Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> select name,open_mode from v$database;

NAME OPEN_MODE

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

ORADB READ WRITE

SQL> show pdbs

CON_ID CON_NAME OPEN MODE RESTRICTED

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

2 PDB$SEED READ ONLY NO

3 PDB1 READ WRITE NO

SQL> alter session set container=PDB1;

Session altered.

SQL> select current_scn from v$database;

CURRENT_SCN

-----------

2782820

SQL> !date

Sat Sep 20 18:44:28 +04 2025

SQL> select * from emp;

ID NAME

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

1 Muthu

[oracle@muthu trace]$ rman target /

Recovery Manager: Release 12.2.0.1.0 - Production on Sat Sep 20 18:47:20 2025

connected to target database: ORADB

RMAN> backup database plus archivelog;

Finished Control File and SPFILE Autobackup at 20-SEP-2025 18:48:26

Thursday, 14 August 2025

Changing the hostname in Linux

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Changing the hostname in Linux depends on your distribution and whether you're using **systemd** (most modern distros do).

1. Check Current Hostname

[root@test ~]# hostnamectl status

Static hostname: test.localdomain

Icon name: computer-vm

Chassis: vm

[root@test ~]# date

Thu Aug 14 15:53:54 +04 2025

[root@test ~]# uptime

15:53:56 up 1 min, 1 user, load average: 2.46, 0.70, 0.24

2. Change Hostname (Permanent)

Using `hostnamectl` (Recommended for systemd-based systems like Ubuntu, CentOS 7+, RHEL 7+, Debian 9+)

sudo hostnamectl set-hostname new-hostname

[root@test ~]# hostnamectl set-hostname muthu.org

> Replace `new-hostname` with your desired name.

3. Update `/etc/hosts`

Edit the file:

sudo nano /etc/hosts

[root@test ~] vi /etc/hosts

Find the line like:

127.0.1.1 old-hostname

And change it to:

127.0.1.1 new-hostname

This ensures local name resolution works properly.

4. Reboot or Re-login

Although the change is immediate, some services may require a reboot:

sudo reboot

[root@test ~]# reboot

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Friday, 5 June 2026

SSH Equivalency Setup in Oracle Exadata – Step-by-Step Guide

Introduction

Environment Details

Step 1: Verify Connectivity

Step 2: Generate SSH Key

Step 3: Copy Public Key to Remote Servers

Step 4: Verify Passwordless Login

Step 5: Configure Reverse Connectivity

Step 6: Validate SSH Equivalency

Step 7: Verify Authorized Keys

Common Issues and Troubleshooting

Permission Denied

Host Key Verification Failed

SSH Timeout

Validation Checklist

Conclusion

Saturday, 18 October 2025

Sunday, 21 September 2025

Saturday, 20 September 2025

Thursday, 14 August 2025

Sample Text

Sample text

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