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Author: Brijesh Gogia

I’m an experienced Oracle Applications DBA with more than a decade of full-time DBA experience. I have gained a wide knowledge of the Oracle software stack and have worked on several big projects for multi-national companies. I enjoy working with the leading-edge technology and have passion for database performance and stability. Thankfully my work allows me time for researching new technologies (and to write about them).
  
You can connect with me on LinkedIn.

Cassandra – 4 – Cassandra Architecture terminology

Cassandra is a distributed database system and it runs on multiple nodes at once.  The nodes use a peer-to-peer communication protocol to exchange any information.

Some key points regarding Cassandra architecture/functioning:

  • Table rows are stored in tables, each with a mandatory primary key
  • Data gets first written to log file for durability and then somewhat similar to RDBMS databases, write the data to cache and when cache is full it write the data finally to disk
  • Automatically partition the data and replicate it.
  • At regular interval, it compacts the data in the database
  • Cluster nodes are chosen randomly to fetch the data as per client need

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Cassandra – 3 – Related Terms : ACID, BASE, CAP Theorem

Oralce/MYSQL database administrators are well aware of term named ACID

ACID stands for: Atomicity, Consistency, Isolation, Durability and it is at the foundation of RDBMS success.

ATOMICITY: If one part of transaction fails, the entire transaction will fail to maintain integrity of database

CONSISTENCY: Database will always be in a consistent state both at the beginning and at the end of a transaction

ISOLATION:  No transaction has access to any other in-flight/unfinished transaction

DURABILITY:  Database records the transaction in persistent storage/data files when it completes. Power/disk  failure will not impact the completed transaction.

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Cassandra – 2 – Basics of Cassandra

The word Cassandra was taken from the name of ancient Greet prophet Cassandra.

Apache Cassandra is a distributed NoSQL database system. It is a distributed database system. It is NOT RDBMS system like Oracle. It is NoSQL database.

High availability and linear scalability are some key benefits of Cassandra database. Cassandra is designed for high-volume, low-latency cloud applications.

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Cassandra – 1 – NoSQL Database

As they say “Necessity is the mother of invention”. There would have been no RDBMS kind of databases like Oracle if there was no computers.

Similarly there would have been no need of NoSQL kind of databases if there was no Internet explosion, no Facebook/social media, no cell phones etc. etc. All these new “trends” generated such huge data at such fast pace that RDMBS was simply not able to cope up. NoSQL helped in solving this problem of this new/huge/versatile/fast generating data.

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Oracle Cloud Infrastructure (OCI) – 3 – Concept of Compartments

To organize your Oracle Cloud resources you will create couple of compartments. Your goal of creating compartment is to have ease of management, security, isolation of resources.

When your tenancy is provisioned, a root compartment is created for you. Your root compartment holds all of your cloud resources.

Before we plan to create a new compartment under our root compartment we should understand some key points and best practices related to compartments.

Some key points that you keep in mind related to compartments are:

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Oracle Cloud Infrastructure (OCI) – 2 – Console

Let us look at the Oracle Cloud Console in this post. Go to https://cloud.oracle.com/en_US/tryit and sign up for the Free Oracle Cloud Promotion. Please note you will need to add your credit card number but it will not be charged.  There is no charge unless you choose to “Upgrade to Paid” from “My Services” console page.

Once your trial account is created you will become a tenant in Oracle Cloud Infrastructure. Oracle will send you a Welcome email which will have userid/password detailed to login to your “tenancy”.

Oracle Cloud Infrastructure supports the latest desktop versions of Google Chrome, Microsoft Edge, Internet Explorer 11, Safari, Firefox, and Firefox ESR. Note that private browsing mode is not supported for Firefox, Internet Explorer, or Edge. Mobile browsers are not supported.

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Oracle Cloud Infrastructure (OCI) – 1 – Fundamentals

Cloud infrastructure is the most basic products delivered by cloud computing companies through the infrastructure as a service (IaaS) model.  You can create your own IT infrastructure complete with processing, storage and networking resources. Cloud Infrastructure companies provide you flexibility in infrastructure design so these infrastructure setups can be easily set up, replaced or deleted as opposed to a physical one, which requires manual work.

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Performance Tuning Basics 16 : Using SQL Tuning Health-Check Script (SQLHC)

This post will cover the SQL Tuning Health Check script basics and how you can use it to collect the key information regarding a poorly performing SQL. SQLHC helps you on focusing on specific SQL and checking Cost-based Optimizer (CBO) statistics, schema object metadata, configuration parameters and other elements that may influence the performance.

Unlike SQLT, this tool SQLHC do not require any code to be installed in the database to provide recommendation. SQLHC uses the SQL_ID of a statement that has already been executed and is in memory to generate the report so it do not actually execute the SQL all lover again. SQLHC works 10g and above. SQLHC is also RAC aware

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Physical and Logical Block Corruption in Oracle Database

Block corruptions are one of the common source of database outages. A database block is corrupted when its content has changed from what Oracle Database expects. Correcting block corruptions can prove to be a lengthy and costly exercise and requires good expertise 0n the DBA part.

Block Corruption can happen at Logical level or Physical level. Also, such corruption can impact a single block or huge number of blocks in the database.

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Performance Tuning Basics 15 : AWR Report Analysis

The Oracle’s Automatic Workload Repository (AWR) collects, processes, and maintains performance statistics for problem detection and self-tuning purposes.  The report generated by AWR is a big report and it can take years of experience to actually understand all aspects of this report. In this post we will try to explain some important sections of AWR, significance of those sections and also some important tips. Please note that explaining all sections of AWR will not be possible so we will stick to some of the most frequently used sections.

Note that this is not comprehensive information and goal is to help in giving an overview of few key sections to Junior DBAs as a primer and to encourage them to build further the knowledge in related fields.

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