Category Archives: BigData

Moving data from oracle to HDFS

I divided the scope into two stages:

Stage -1 | Initial data load from Oracle database to HDFS (for bulk load)

  • Here I used oracle native utility (Copy2hadoop) for reducing the friction

Stage -2 | Synchronize data from Oracle to Hadoop (delta changes)

  • Here I used SharePlex, comparatively effective third party tool (Quest/Dell) for data replication

Stage -1 | Initial data load from Oracle database to HDFS

Generally, we have two tools for data movement from the Oracle Database to HDFS

Sqoop and Copy2Hadoop :

Copy2Hadoop has advantages over sqoop, In my case we have complex query(Functions, PL/SQL, Joins) or even views (like a sub-case for complex queries). So, it is recommended to use Copy2Hadoop for the initial load. Since it is oracle native utility it will save our time and effort.

Copy2Hadoop creates datapump files that could have any Oracle datatype which is supported by Oracle External table and store data in Oracle’s datatype. When we convert datatype from Oracle format to the Java format (like sqoop does) there is always risk that some information would be converted incorrectly. Copy2Hadoop insures us from that.

Below are the high-level steps to copy the data:

Create Oracle Data Pump files from Oracle Database table data that we want to move. 
We can do this by exporting the data from the Oracle Database table using the oracle_datapump
access driver (Using Oracle Data Pump files generated by other database utilities will
not be accessible by Hive tables.  We need to use the oracle_datapump access driver to export the data.)

• Create Oracle Data Pump files and the ORACLE_DATAPUMP access driver.

• Copy the Oracle Data Pump files from source system to HDFS.

• Create Hive tables to read the Oracle Data Pump files.

What Is Copy to Hadoop?
Oracle Big Data SQL includes the Oracle Copy to Hadoop utility. This utility makes it simple to identify and copy Oracle data to the Hadoop Distributed File System. It can be accessed either through a command-line interface or via Oracle SQL Developer. Data exported to the Hadoop cluster by Copy to Hadoop is stored in Oracle Data Pump format. This format optimizes queries thru Big Data SQL:

• The data is stored as Oracle data types – eliminating data type conversions

• The data is queried directly – without requiring the overhead associated with Java SerDes

After generating Data Pump format files from the tables and copying the files to HDFS, you can use Apache Hive to query the data. Hive can process the data locally without accessing Oracle Database. When the Oracle table changes, you can refresh the copy in Hadoop. Copy to Hadoop is primarily useful for Oracle tables that are relatively static, and thus do not require frequent refreshes.

Copy to Hadoop is licensed under Oracle Big Data SQL. You must have an Oracle Big Data SQL license in order to use utility

Stage -2 | Synchronize data from Oracle to Hadoop

Using SharePlex to replicate the data in near real-time.

What is SharePlex ?

SharePlex is the complete enterprise solution for Oracle database replication, including high availability, scalability, data integration and reporting use cases.

Why SharePlex ?

• Redo Log Based Database Replication
• Read the redo log for changes
• Ship the changes from source to target in near-real time
• Requires source and target have identical data to start
• Backup/copy consistent to an SCN
• Maintain synchronization between databases

SharePlex architecture

Using Kafka Connect to Capture Data from a Relational Database (sqlite3)

Use any Kafka docker images to install and start kafka.


JDBC driver download for SQLlite3:

  • Start Kafka.
confluent start
  • Install SQLite3.
apt-get update
apt-get install sqlite3
  • Create a New Database and Populate It with a Table and Some Data
    Create a new database called “test.db”.
root@shanoj_srv1:/# sqlite3 test.db
  • Create a new table in the SQLite database called “accounts”.
name VARCHAR (255));
  • Insert values into the table to begin populating it.
INSERT INTO accounts(name) VALUES('sabu');
INSERT INTO accounts(name) VALUES('ronnie');
  • Stop Kafka Connect.
confluent stop connect
  • Make necessary changes to below files:
root@shanoj_srv1:/# vi /etc/schema-registry/

# The internal converter used for offsets and config data is configurable and must be specified,

# Local storage file for offset data
root@shanoj_srv1:/# vi etc/kafka-connect-jdbc/

# A simple example that copies all tables from a SQLite database. The first few settings are
# required for all connectors: a name, the connector class to run, and the maximum number of
# tasks to create:
# The remaining configs are specific to the JDBC source connector. In this example, we connect to a
# SQLite database stored in the file test.db, use and auto-incrementing column called 'id' to
# detect new rows as they are added, and output to topics prefixed with 'test-sqlite-jdbc-', e.g.
# a table called 'users' will be written to the topic 'test-sqlite-jdbc-users'.
  • Start Kafka Connect in standalone mode.
root@shanoj_srv1:/#connect-standalone -daemon /etc/schema-registry/ /etc/kafka-connect-jdbc/
  • Verify that the connector was created.
root@shanoj_srv1:/# cat /logs/connectStandalone.out | grep -i "finished"
[2019-08-15 15:45:49,421] INFO Finished creating connector test-source-sqlite-jdbc-autoincrement (org.apache.kafka.connect.runtime.Worker:225)
[2019-08-15 15:45:49,504] INFO Source task WorkerSourceTask{id=test-source-sqlite-jdbc-autoincrement-0} finished initialization and start (org.apache.kafka.connect.runtime.WorkerSourceTask:143)
[2019-08-15 15:46:49,484] INFO Finished WorkerSourceTask{id=test-source-sqlite-jdbc-autoincrement-0} commitOffsets successfully in 6 ms (org.apache.kafka.connect.runtime.WorkerSourceTask:373)
root@shanoj_srv1:/# curl -s localhost:8083/connectors
  • Examine the Kafka topic created.
root@shanoj_srv1:/# kafka-topics --list --zookeeper localhost:2181 | grep test-sqlite-jdbc

Start a Kafka Consumer and Write New Data to the Database

  • Open a Kafka consumer.
root@shanoj_srv1:/# kafka-avro-console-consumer --new-consumer --bootstrap-server localhost:9092 --topic test-sqlite-jdbc-accounts --from-beginning

Open a new tab to a new terminal session.
Open a new shell in this session.

root@shanoj_srv1:/# sudo docker exec -it sqlite-test //bin//bash
  •  Transfer to the tmp directory.
root@shanoj_srv1:/# cd /tmp
  • Access the SQLite database test.db.
root@shanoj_srv1:/# sqlite3 test.db
  • Insert a new value into the accounts table.
root@shanoj_srv1:/tmp# sqlite3 test.db
SQLite version 2014-10-29 13:59:56
Enter ".help" for usage hints.
sqlite> INSERT INTO accounts(name) VALUES('rama');
sqlite> INSERT INTO accounts(name) VALUES('lev');
sqlite> INSERT INTO accounts(name) VALUES('sriram');
sqlite> INSERT INTO accounts(name) VALUES('joby');
sqlite> INSERT INTO accounts(name) VALUES('shanoj');
  • Return to the previous session with the consumer and verify the data has been written.
root@ip-10-0-1-100:/# kafka-avro-console-consumer --new-consumer --bootstrap-server localhost:9092 --topic test-sqlite-jdbc-accounts --from-beginning

Install and Configure PostgreSQL 9.x: RHEL/CentOS

1.Download and install it using the appropriate package management

~ $ rpm -Uvh
warning: /var/tmp/rpm-tmp.IZow7N: Header V4 DSA/SHA1 Signature, key ID 442df0f8: NOKEY
Preparing... ################################# [100%]
Updating / installing...
1:pgdg-redhat-repo-42.0-4 ################################# [100%]

2. Applying any necessary updates.

[root@tcox6 ~]# yum update

3. Install the PostgreSQL 9.4 server and associated contribed modules and utilities. Once installed, run the database initialization routine before starting the database.

[root@tcox6 ~]# yum install postgresql94-server postgresql94-contrib

4. Enable the PostgreSQL 9.4 server to run on system start and then start the database server.

[root@tcox6 ~]# systemctl enable postgresql-9.4

ln -s '/usr/lib/systemd/system/postgresql-9.4.service' '/etc/systemd/system/'

[root@tcox6 ~]# systemctl start postgresql-9.4

5. Check to see if SELinux is being run in enforced mode on your system. If so, run the command to allow external HTTP DB connections to the server through SELinux configuration.

# cat /etc/selinux/config

# This file controls the state of SELinux on the system.

# SELINUX= can take one of these three values:

#     enforcing - SELinux security policy is enforced.

#     permissive - SELinux prints warnings instead of enforcing.

#     disabled - No SELinux policy is loaded.


# SELINUXTYPE= can take one of these two values:

#     targeted - Targeted processes are protected,

#     minimum - Modification of targeted policy. Only selected processes are protected.

#     mls - Multi Level Security protection.


# setsebool -P httpd_can_network_connect_db 1

6. Login to the ‘postgres’ user and run the ‘psql’ command. Once at the database prompt, set a password for the ‘psql’ user.

[root@tcox6 ~]# su - postgres

Last login: Wed Sep  2 13:35:21 UTC 2015 on pts/0

-bash-4.2$ psql

psql (9.4.4)

Type "help" for help.


postgres=# \password postgres

Enter new password:

Enter it again:

postgres=# quit

postgres-# \q

-bash-4.2$ exit




Hadoop Installation with Single DataNode on Ubuntu (VirtualBox)

Download link!

The above document contains :

01) Updating the Ubuntu repository.
02) Installing openjdk-6-jdk.
03) Installing openssh-server.
04) Downloading and installing Hadoop.
05) Configuring Hadoop enveronment.
07) Create a ssh key.
08) Format the name node
09) Start the namenode, datanode
10) Start the task tracker and job tracker.
11) Checking if Hadoop started correctly.