Cassandra - Introduction

<<Back to Cassandra Main Page

Cassandra - Introduction

What is Cassandra

Apache Cassandra is a NoSQL Database. It is highly scalable, high-performance and distributed database designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure.

In the definition we used many terms like NoSQL, Commodity Server etc. Let us understand these terminology one by one to understand the Cassandra definition

NoSQL Database

A NoSQL database is a database that provides a mechanism to store and retrieve data in non-relational format (as oppose to RDBMS Database)
These databases are schema free, can handle huge amount of data and support easy replication to support fault tolerance. NoSQL Database does not support transactions and it is eventually consistent (while RDBS database follows ACID (Atomicity, Consistency, Isolation, and Durability)).
Beside Cassandra there are many NoSQL database platforms available in the market such as

1.Apache Spark
2.Apache Storm
3.Google BigQuery
4.Ceph
5.DataTorrent RTS
6.Disco
7.Pachyderm
8.Presto
9.Hydra
10.Misco
11.Qizmt
12.MongoDB
etc...etc....

Commodity Hardware?

Commodity Hardware is really inexpensive affordable and easy to obtain Computers.

Features of Cassandra

Cassandra offers verity of features which makes it one of the popular NoSQL database among others. Below are the highlights of Features offered by Cassandra

Fast writes - Cassandra performs fast writes and can store hundreds of terabytes of data without compromising the read efficiency.

Easy data distribution - Cassandra provides the flexibility to distribute data where you need by replicating data across multiple data centers.

Elastic scalability - Cassandra is highly scalable. it allows to add more hardware to accommodate more customers and more data as per requirement.

Always on architecture - Cassandra provides high availability. It has no single point of failure and it is continuously available for business-critical applications.

Fast linear-scale performance - Cassandra is linearly scalable, i.e., it increases your throughput as you increase the number of nodes in the cluster.

Flexible data storage - Cassandra accommodates all possible data formats including: structured, semi-structured, and unstructured. It can dynamically accommodate changes to your data structures according to your need.

Comments

How to Power On/off Oracle Exadata Machine

<<Back to Exadata Main Page How to Power On/off Oracle Exadata Machine Oracle Exadata machines can be powered on/off either by pressing the power button on front of the server or by logging in to the ILOM interface. Powering on servers using button on front of the server The power on sequence is as follows. 1. Start Rack, including switches Note:- Ensure the switches have had power applied for a few minutes to complete power on configuration before starting Exadata Storage Servers 2.Start Exadata Storage Servers Note:- Ensure all Exadata Storage Servers complete the boot process before starting the database servers 3. Start Database Servers Powering On Servers Remotely using ILOM The ILOM can be accessed using the Web console, the command-line interface (CLI), IPMI, or SNMP. For example, to apply power to server dm01cel01 using IPMI, where dm01cel01-ilom is the host name of the ILOM for the server to be powered on, run the

ORA-28374: typed master key not found in wallet

<<Back to Oracle DB Security Main Page ORA-46665: master keys not activated for all PDBs during REKEY SQL> ADMINISTER KEY MANAGEMENT SET KEY FORCE KEYSTORE IDENTIFIED BY xxxx WITH BACKUP CONTAINER = ALL ; ADMINISTER KEY MANAGEMENT SET KEY FORCE KEYSTORE IDENTIFIED BY xxxx WITH BACKUP CONTAINER = ALL * ERROR at line 1: ORA-46665: master keys not activated for all PDBs during REKEY I found following in the trace file REKEY: Create Key in PDB 3 resulted in error 46658 *** 2019-02-06T15:27:04.667485+01:00 (CDB$ROOT(1)) REKEY: Activation of Key AdnU5OzNP08Qv1mIyXhP/64AAAAAAAAAAAAAAAAAAAAAAAAAAAAA in PDB 3 resulted in error 28374 REKEY: Keystore needs to be restored from the REKEY backup.Aborting REKEY! Cause: All this hassle started because I accidently deleted the wallet and all wallet backup files too and also forgot the keystore password. There was no way to restore the wallet back. Fortunately in my case the PDB which had encrypted data was supposed to be deco

How to Find VIP of an Oracle RAC Cluster

<<Back to Oracle RAC Main Page How to Find Out VIP of an Oracle RAC Cluster Login clusterware owner (oracle) and execute the below command to find out the VIP hostname used in Oracle RAC $ olsnodes -i node1 node1-vip node2 node2-vip OR $ srvctl config nodeapps -viponly Network 1 exists Subnet IPv4: 10.0.0.0/255.255.0.0/bondeth0, static Subnet IPv6: Ping Targets: Network is enabled Network is individually enabled on nodes: Network is individually disabled on nodes: VIP exists: network number 1, hosting node node1 VIP Name: node1-vip VIP IPv4 Address: 10.0.0.1 VIP IPv6 Address: VIP is enabled. VIP is individually enabled on nodes: VIP is individually disabled on nodes: VIP exists: network number 1, hosting node node2 VIP Name: node2-vip VIP IPv4 Address: 10.0.0.2 VIP IPv6 Address: VIP is enabled. VIP is individually enabled on nodes: VIP is individually disabled on nodes:

ORA-16905: The member was not enabled yet

<<Back to Oracle DataGuard Main Page ORA-16905 Physical Standby Database is disabled DGMGRL> show configuration; Configuration - DG_ORCL1P Protection Mode: MaxPerformance Members: ORCL1PP - Primary database ORCL1PS - Physical standby database (disabled) ORA-16905: The member was not enabled yet. Fast-Start Failover: Disabled Configuration Status: SUCCESS (status updated 58 seconds ago) DGMGRL> DGMGRL> enable database 'ORCL1PS'; Enabled. DGMGRL> show configuration; Configuration - DG_ORCL1P Protection Mode: MaxPerformance Members: ORCL1PP - Primary database ORCL1PS - Physical standby database Fast-Start Failover: Disabled Configuration Status: SUCCESS (status updated 38 seconds ago)

How to Switch Log File from All Instances in RAC

<<Back to Oracle RAC Main Page Switch The Log File of All Instances in Oracle RAC. In many cases you need to switch the logfile of the database. You can switch logfile using alter system switch logfile command but if you want to switch the logfile from all the instances you need to execute the command on all the instances individually and therefore you must login on all the instances. You can avoid this and switch logfile of all instances by just running the below command from any of the instance in RAC database SQL> ALTER SYSTEM SWITCH ALL LOGFILE; System altered.

ORA-65104: operation not allowed on an inactive pluggable database alter pluggable database open

<<Back to DB Administration Main Page ORA-65104: operation not allowed on an inactive pluggable database SQL> alter pluggable database TEST_CLON open; alter pluggable database TEST_CLON open * ERROR at line 1: ORA-65104: operation not allowed on an inactive pluggable database Cause The pluggable database status was UNUSABLE. It was still being created or there was an error during the create operation. A PDB can only be opened if it is successfully created and its status is marked as NEW in cdb_pdbs.status column SQL> select PDB_NAME,STATUS from cdb_pdbs; PDB_NAME STATUS -------------------- --------------------------- PDB$SEED NORMAL TEST_CLON UNUSABLE Solution: Drop the PDB and create it again. Related Posts How to Clone Oracle PDB (Pluggable Database) with in the Same Container

ORA-46630: keystore cannot be created at the specified location

<<Back to DB Administration Main Page ORA-46630: keystore cannot be created at the specified location CDB011> ADMINISTER KEY MANAGEMENT CREATE KEYSTORE '+DATAC4/CDB01/wallet/' IDENTIFIED BY "xxxxxxx"; ADMINISTER KEY MANAGEMENT CREATE KEYSTORE '+DATAC4/CDB01/wallet/' IDENTIFIED BY "EncTest123" * ERROR at line 1: ORA-46630: keystore cannot be created at the specified location Cause Creating a keystore at a location where there is already a keystore exists Solution To solve the problem, use a different location to create a keystore (use ENCRYPTION_WALLET_LOCATION in sqlnet.ora file to specify the keystore location), or move this ewallet.p12 file to some other location. Note: Oracle does not recommend deleting keystore file (ewallet.p12) that belongs to a database. If you have multiple keystores, you can choose to merge them rather than deleting either of them.

Starting RMAN and connecting to Database

<<Back to Oracle Backup & Recovery Main Page Starting RMAN and connecting to Database Starting RMAN and connecting to Database To start RMAN you need to set the environment and type rman and press enter. You can connect to database either using connect command or using command line option. using command line option localhost:$ export ORACLE_HOME=/ora_app/product/18c/dbd2 localhost:$ export PATH=$ORACLE_HOME/bin:$PATH localhost:$ export ORACLE_SID=ORCL1P localhost:$ rman target / Recovery Manager: Release 18.0.0.0.0 - Production on Sun Apr 4 08:11:01 2021 Version 18.11.0.0.0 Copyright (c) 1982, 2018, Oracle and/or its affiliates. All rights reserved. connected to target database: ORCL1P (DBID=4215484517) RMAN> using connect option localhost:$ rman RMAN> connect target sys@ORCL1P target database Password:******** connected to target database: ORCL1P (DBID=4215484517) NOTE: To use connect command you need to ensure that you have proper TNS sentry for database (ORCL

How to Attach to a Datapump Job and Check Status of Export or Import

<<Back to Oracle DATAPUMP Main Page How to check the progress of export or import Jobs You can attach to the export/import job using ATTACH parameter of oracle datapump utility. Once you are attached to the job you check its status by typing STATUS command. Let us see how Step1> Find the Export/Import Job Name You can find the datapump job information from DBA_DATAPUMP_JOBS or USER_DATAPUMP_JOBS view. SQL> SELECT OWNER_NAME,JOB_NAME,OPERATION,JOB_MODE,STATE from DBA_DATAPUMP_JOBS; OWNER_NAME JOB_NAME OPERATION JOB_MODE STATE ---------- ------------------------------ -------------------- ---------- ---------- SYSTEM SYS_EXPORT_FULL_02 EXPORT FULL EXECUTING OR You can also find the job name for export/import in logfile in beginning itself. Step2>Attach to the Job and check status One you get the Export/Import Job Name attach the job and check its status. You can attach or det

Step by Step how to Create Virtual Machine using Virtualbox

<<Back to Linux Main Page How to Create New Virtual Machine Using Oracle Virtual Box Step1: Open Oracle Virtual Box --> Click New Provide Name, Type and Version as shown in the image below and click Next Step2: Adjust memory (RAM) as per the requirement and availability and click Next. NOTE:- Remember to leave enough memory for the host OS to work properly. Step3: Select the option to create a new virtual hard drive and click "Create" (erzeugen) button. Step4: Accept Default and click next (weiter) Step5: Accept the dynamically allocated option by clicking the "Next" (weiter) button. Step6: If you don't want to use the defaults, enter the required location, name and size of the virtual disk and click the "Create" (erzeugen) button. Note:- At this point your virtual machine is created and ready for OS installation Preparing the Virtual machine for Oracle RAC Installation Step1: Select t

Online DBA

Search This Blog