Category Archives: Database

AWS Error 2003 – Can’t Connect to RDS MySQL Server

rds mysql database page

In this post, you will learn about the solution to the error, AWS Error 2003: Can’t Connect to RDS MySQL Server, which you may come across while trying to connect AWS MySQL RDS server from your local machine (laptop or desktop). I came across this error when I first created an RDS MySQL instance using AWS console and tried accessing the instance from my laptop using the command such as mysql -h endpoint_address -P 3306 -u username -p. The following represents the error: As a matter of fact, I have come across this error once in a while trying to connect the MySQL database app from the command prompt or the application. The solution works …

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Posted in AWS, Database. Tagged with , .

DynamoDB – Partition Key vs Composite Partition Key

dynamodb partition key vs composite primary key

AWS DynamoDB has two key concepts related to table design or creating new table. A beginner with DynamoDB is found to be wondering on whether to use a partition key or composite partition key when creating a new table. Composite partition key is also termed as composite primary key or hash-range key. In this post, you will learn about some of the following: Is the partition key same as the primary key of a table? What are composite partition key or composite primary key? When to use partition key vs composite partition key? This post presumes that you have got a good understanding of partition concept and how DynamoDB stores …

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Posted in AWS, Database. Tagged with .

Consistent Hashing Concepts – Databases, DHT

Consistent Hashing Ring

This blog represents What’s The Funda (WTF) around consistent hashing  and DHT (Distributed Hash Tables), Databases use cases where it is used. Problems with Traditional Hashing Mechanism Lets understand the traditional hashing mechanism using following diagram: Pay attention to some of the following aspects as per the above diagram: Hash table/map is an array with each of the array index pointing to a linked list having each node representing a key-value pair. Keys are passed through a hash function. The index of the array (bucket) to which a specific key-value pair would get associated is a function of hash value and total size of the array. For example, in above diagram, key such as “Sam …

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Posted in Data Structure, Database. Tagged with , .

Dummies Notes – How to Setup Oracle Data Guard

This article represents instructions which could be used to set up oracle data guard on a primary and one or more physical standby database. The article presumes that you have a basic understanding of what is Oracle Data guard and why it needs to be set up. Following are key aspects which are discussed later in this article: Primary Database Setup Physical Standby Database Setup Following is details on primary and physical standby database setup: Primary Database Setup: Configure the primary database appropriately including doing some of the following: Enable force logging Alter the database parameters such as following. This is one time activity and does not needed to be …

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Posted in Database. Tagged with , .