The Hadoop Distributed File System (HDFS) is a highly fault tolerant file system designed and optimized to be deployed on a distributed infrastructure established with a bunch commodity hardware. HDFS provides high throughput access to application data and is best suited for applications that have large data sets. Unlike existing distributed file systems HDFS have loosen up a few POSIX Standards to enable streaming access to file system data. HDFS was originally developed as an infrastructure for the Apache Nutch web search engine project.

In this article we have tried to summaries, how a MapReduce program executes in Hadoop environment.

Back in 1969, UNIX has evolved through a number of different versions and environment. One of the Original UNIX editors has licensed the most modern UNIX variants. It's closed Source software. There are various flavors of UNIX are available in market like Sun's Solaris, Hewlett-Packard's HP-UX, and IBM's AIX all of these have their own Unique Foundation, all these flavors are optimized and incorporated with different tools which are most compatible with their hardware.

Linux is an open source (free to use and redistribute under GNU licenses) operating system widely used for computer hardware and software, game development, tablet PCS, mainframes etc. UNIX is a copyrighted name only big companies (IBM, HP etc…) are allowed to use the UNIX copyright and names. UNIX is commonly used in internet servers, workstations and PCs by Solaris, Intel, and HP etc.

I have seen people writing number of lines of code to find out the date on a specific day in current or previous week, most often we need Friday the last working day of the week. We have a pretty simple way to find out in Oracle Queries.