MongoDB Recording of write operations in journal

MongoDB does make sure of journal files which are physical files stored in disks to perform crash recovery in case of unexpected shutdown if mongod daemon. Journal files stores the following information that are typically considered write operations in a mongoDB environment
1) Changes to collection including updates of documents, inserted documents
2) Changes to index structures
3) Changes made to the namespace files. This includes metadata changes to namespace files. Say we have a database by name learnersreference, the data directory contians files of form learnersreference.0,learnersreference.1…learnersreference.n,journal[journal file], learnersreference.ns[namespace datafile]
3) Information on database changes including creation, dropping od databases, their associated datafiles etc
How does a mongoDB record write operation in journal file?
1) Whenever there is a write operation mongoDB copies these onto the private view which is a storage view in Physical RAM
2) MongoDB then writes these in batches called group commits onto journal files. This is tunes by appropriately setting commitIntervalMs parameter. When the group commit happens all the writers are blocked
3) From journal file mongoDB writes the information onto the shared view which is the operating system virtual memory view. This leaves shared view in a state different than the datafiles. This state is by default retained for 60 seconds. IF there is a memory crunch then there is a possibility to have this frequency changed from 60 seconds to littel less. After this timing information from shared view is written onto datafiles on disk
4) At this point all the jounal writes have been flushed
5) MongoDB stores details on write operations flushed onto datafiles. This information in journalfile is no longer necessary. Hence the journal file is recycled or deleted

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Schema difference NosQL Vs RDBMS

NoSQL the new generation databases are gaining popularity with storing, processing of big data. Traditional information data stores happened to be relational database management systems. Here is a quick overview of difference in schema design between RDBMS and NoSQL databases
1) RDBMS schema design – Fixed schema. Once a table is created with columns containing specified datatype, information needs to be stored in all columns with designated datatype
2) NoSQL schema design – Dynamic schema. There is no need for every field to contain data. Also the type of data stored in a field can vary

MongoDB Journaling an Overview

MongoDB stores information as data in datafiles. Journaling mechanism offers write-protect mechanism in MongoDB. Journal files are physical files stored in physical disk location
1) Data changed in RAM is written onto journal file on disk
2) Information from Journal file is applied to data files
3) In case of mongod daemon crash, information is retained in journal file
4) After a crash, information is applied from journal file
5) By default 100ms worth of information is lost as this is the default commitintervalMs. This setting is the value that determines the timing between data writes onto journal files from memory. This setting can be changed
6) Without a journal file in place, when a mongod crashes we need to perform repair (or) resync from clena member of replica set if one in place
7) From MongoDB 2.2 onwards in 64-bit environment journaling is enabled by default

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Vormetric application encryption a quick overview

Enterprise security is gaining popularity day by day. With advent of standards like HIPPA, PCI DSS security of data at every level does become important. Cost of losing a data is much more than securing the data. Addressing such needs is now possible using enterprise grade security solutions. One such solution is Vormetric transparent encryption. It meets enterprise security, contractual requirements, compliance requirements by application of encryption, access policies. This is used with databases, big data, Platform as a service aka PaaS to secure data residing at rest in disk.
One interesting application that does provide document and field level encryption is MongoDB.Vormetric Application Encryption is a library to simplify integrating application-level encryption into existing corporate applications. Vormetric data security platform can be used with mongoDB to provide OS, file and application level encryption

MongoDB 2.8 Release Candidate Released November 13 2014 Start Bug Hunt

Mongodb 2.8 Release Candidate aka RC has been released by MongoDB on November 13th 2014. With this release mongodb has announced bug hunt in progress for next 3 weeks. As per MongoDB here are some interesting features of 2.8
1) Pluggable Storage Engines – WiredTiger is the latest storage engine that supportsĀ burn through write-heavy workloads
2) Improved Concurrency- As opposed to database level locking in prior versions, 2.8 supports document level locking
3) Snappy compression offers improved
Download the latest version Mongodb 2.8 RC to start your bug hunt today

Latest production mongodb 2.6.5 version

MongoDB 2.6.5 is the latest production version of mongoDB. IT is officially available for download in mongoDB website. This has been released on october 8,2014. MongoDB 2.6.5 is available to download for the following versions.
1) Linux
2) Solaris
3) Windows
4) MAcOS
Latest version of mongodb 2.7.8 is in development as of october 22,2014 as per the mongoDB it is still to be used with development but not a formal stable production build

Big Data Predictive Analysis In Healthcare

Healthcare the domain often considered evergreen has tremendous amount of data and will generate more data as population keeps growing day by day. Information often gets generated in unstructured format in form of clinical notes, radiology records, PACS reports, images, genetic reports etc. As a result the need to store healthcare data in form of big data in NoSQL databases becomes inevitable.
How does predictive analysis play role in healthcare?
Prediction is no different than diagnosing a health condition. Predictive analysis is the process to determine the pattern among the existing information that provides more insight on possible chronic health conditions. One such example is prediction of heart disease by analyzing the current range of a certain compound in blood results.
What is essential to find new job opportunities in this domain?
Basic knowledge of IT
Healthcare domain terminologies like ehr,pacs, dicom to name a few
NoSQL databases that support big data. One such example is mongodb
Hadoop framework

Commands in mongodb 2.6

As with any other database MongoDB is a NoSQL database in which informaiton is stored, retrieved, manipulated. This is accomplished using CRUD commands – Create, Read, Update and delete. In addition to this MongoDB offers advanced features in form of MongoDB commands
So, what is a mongoDB command?
to implement functionality that falls outside scope of CRUD mongodb makes use if commands. They assist with many different operations of mongoDB collections
Some popular MongoDB commands include :
1) getlasterror()
2) db.runcommand({“drop”:”collectionname”); – This is a good example of drop command
MongoDB supports many such commands
How do I ge tlist of commands from MongoDB?
To get to know list of commands supported by particular version of MongoDB run :