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Decommission a Data-Center In Cassandra

In this post, we will discuss how to decommission a Data center in Cassandra. Prerequisites to Decommission a Data Center:- Make sure no clients are still writing to any nodes in the data center. All traffic should move to other data center. Comment all cron-job/script which restart Cassandra and repairRead More

Cassandra: An Insights of G1GC log

This is the third post related to Garbage Collection in Cassandra. In this post we will discuss how to read G1GC log. I have already posted about enabling G1GC log in previous post. Minor GC Event:- Whenever a minor GC events occured, gc log prints below.  2020-03-13T16:15:03.803-0500: 18.259: [GC pauseRead More

Cassandra 3.0 or later: Enable GC logging

  This is the second post related to Garbage Collection in Cassandra. In this post we will discuss how can we enable GC logging with G1 or CMS Garbage Collector. I already discussed pros/cons of G1/CMS Garbage Collector in previous post. To enable the GC logs, and other parameters relatedRead More

Cassandra: Garbage Collector Introduction

In this blog post we will discuss about Garbage Collection with respect to Cassandra 3.0 or later. Optimizing Garbage Collection is very important in Cassandra. It can improve performance ~5 times performance and save huge money. What is Garbage Collection? Garbage collection also known as GC is an important featureRead More

Amazon Managed Cassandra Service(MCS)

  AWS Announced Amazon Managed (Apache) Cassandra Service (MCS):- AWS confirmed Amazon Managed Apache Cassandra Service (MCS) at AWS: reinvent 3rd Dec’19. Amazon Managed Cassandra Service provides high availability, scalability and Apache Cassandra compatible database service which is also server-less. AWS has many customers who asked to have managed CassandraRead More

WARN : “Mutation of xxx bytes is too large for the maximum size of xxx”

  In this blog post, we will explain the error of “Mutation of xxx bytes is too large for the maximum size of xxx”. Recently, we encountered an error(WARN) “Mutation of 17156436 bytes is too large for the maximum size of 16777216”. To understand the above error, we should know whatRead More

Upgrade Config Server to Replica Set

Upgrade Config Servers to Replica Set Only upgrade Mirrored config servers (SCCC) to CSRS if all members of the mongod config instance are at least v3.2.4. The existing config server must be in sync. To check config server is in sync or not- We shouldn’t get mongod config logs like- ERROR: configRead More

Configure 3 member replica set with RBAC

To Configure 3 member replica set, I have configured 3 virtual box for demonstration purpose. These are below steps to configure it. Step 1. Make directories for data, log, config file, keyfile  in each members of replica set. Data directory will store the actual data files, log directory will store theRead More

How Cassandra Reads the data?

  To Satisfy read/write request, it must achieve consistency level (whatever we define, either CL = 1, 2 or Quorum. To know more, please check consistency level). To complete the read request, Cassandra combine the request set of active MemTable and SSTables. Cassandra fetch data from multiple stages to discoverRead More

Reconfigure Grid Infrastructure on Standalone Environment (

De-configure has: [root@DG2 ~]# /u01/app/ /u01/app/ -deconfig -force Using configuration parameter file: /u01/app/ CRS-4639: Could not contact Oracle High Availability Services CRS-4000: Command Stop failed, or completed with errors. CRS-4639: Could not contact Oracle High Availability Services CRS-4000: Command Delete failed, or completed with errors. CLSU-00100: Operating System function: opendirRead More

Oracle database upgradation using dbua with silent method( to

[oracle@OEL6:/home/oracle]: dbua -silent -sid OELTEST -sysDBAUserName sys -sysDBAPassword xxxxx Log files for the upgrade operation are located at: /u01/app/oracle/cfgtoollogs/dbua/OELTEST/upgrade2 Performing Pre Upgrade 1% complete 7% complete Upgrading Oracle Server 7% complete 8% complete 9% complete 10% complete 10% complete 11% complete 12% complete 12% complete 13% complete 14% complete 15%Read More

Oracle Enterprise Manager Cloud control 12c Relase 5 ( Installation on Linux Environment

OS Prerequisites: First we need to check OS level pre-requisites on OMS host. Following packages are necessary for the cloud control installation: # OL5 and OL6 yum install make -y yum install binutils -y yum install gcc -y yum install libaio -y yum install glibc-common -y yum install libstdc++ -yRead More

Oracle10g client Installation on Linux/AIX environment using silent Method

Below are the default templates (response files) available for client installation: clientadmin.rsp    clientcustom.rsp   clientruntime.rsp  instantClient.rsp For admin Installation, we need to use clientadmin.rsp file and update the below entries in response file: UNIX_GROUP_NAME ORACLE_HOME ORACLE_HOME_NAME (if already HOME exist) $ ./runInstaller -silent -responsefile /apps/oracle10g_client/dvd2/client/response/clientadmin.rsp Starting Oracle Universal Installer… No pre-requisiteRead More

How Cassandra Writes Data?

How can we say Data has been written successfully? Cassandra writes data in 4 stages. When Application send request to write data, there is a coordinator which actually hash the data( it’s partitioner role) and create a token and then coordinator identify this token range belongs to which node and itRead More

Different ways to start and stop DB Services

There are many ways to start and stop DB services in SQL Server. Here I am writing down most frequently used in real time by DBA.       Using SQL Server Configuration Manager                                  Read More

Different states/Modes of database in SQL Server

In this article, I want to explain about different states or sometimes we call modes of database in SQL Server. We have different modes of database in SQL Server. These are mentioned below. I will go through each mode one by one. Online Mode Offline Mode Restoring Mode Recovery Mode RecoveryRead More

Recovering database from suspect mode

Recently I got an issues in one of the database in production environment where I found a database is in suspect mode. It happens some time because of services re-start activity which happened in my case. In such scenarios, we need to repair the database to make it online. TheseRead More

Kill Long Running Queries

To Kill Long Running Queries:- Many people asked me how can we kill long running queries in one shot, as they have to find the long running queries one by one and then they kill, which is time taking. I’ve written this Java Script, it actually find the slow queriesRead More

Installation of SQL Server 2012 on Windows

Installation of SQL server 2012 Enterprise Edition on Windows To install SQL Server 2012, we need to follow below mentioned steps: step 1: Go to the location where setup file of SQL Server is kept. Right click on the setup file and run this as an administrator. Step 2: InstallationRead More

Backup a Sharded Cluster

This article will help you to take sharded cluster backup. To take backup of sharded cluster, we will use mongodump from mongod running server, we can also use File System-Snapshot to capture the data. Procedure To take backup To create backups of a sharded cluster, we need to stop theRead More