This would also mean that the shadowing process goes on behind the scenes, and one need not even be aware that the process is in fact going on at any point of time; it can go on without creating any sort of disturbance to the user of the application, at any point of time. (Shadow Files)
Another important advantage of using the shadowing of a database is that data would be immediately available, even when the primary database has failed due to some reason or another. Non-exclusive usage of the primary database is also permitted, and this means that the database will not be locked, and this in turn means that it can be updated and changed during the process of its creation. Computer resource can be conserved, and this is because of the fact that shadowing does not use any separate process; the database process gives the shadow database the function of updating its own database. (Sygate Secure Enterprise, 4.0)
There can be certain disadvantages when creating a shadow for one's primary database, and some of them are as follows: not all types of conflicts can be detected, and some updates can even get lost due to undetected reasons. (Critical Data Availability in Real time.) Another great disadvantage of using shadowing is that all the data tends to become quite declustered after some time. (Write Optimized Object Oriented Database Systems) Since today's working environment dictates that there must be total and complete data recovery after a crash or a failure, all businesses are in fact making serious attempts to protect themselves and each other from data loss, and this is one of the benefits of using a shadow as a back up whenever and wherever required.
However, some people do opine that these are not adequate solutions and that if a regional disaster or an outage were to occur, then it is not an exaggeration to state that the entire production may get affected by it. The Remote Data recovery Facility used by several companies all over ensures that the relevant data is not only well protected but is also insulated against...
This is an excellent solution for the read only functions like, for example, data warehousing and mining, batch reporting cycles, complex and complicated SQL queries, load balancing, and local online access at the site of the shadow. Information and data can be safeguarded and protected using the system of shadows for database applications. (Data Recovery without data loss)
References
Database Shadowing System with data tags that select an operation of the save command"
Retrieved at http://www.freepatentsonline.com/5230075.html. Accessed 4 October, 2005
Data Recovery without data loss" Retrieved at http://www.enet.com/enet.com.nsf/PAGES_RRDF_Recov.html?OpenPage&charset=iso-8859-1Accessed 4 October, 2005
Eng, Audra. (July, 2004) "Sygate Secure Enterprise, 4.0" Retrieved at http://www.sygate.com/solutions/datasheets/wp/WP-Sygate-Secure-Enterprise.pdf. Accessed 4 October, 2005
Flesher, Tom. (19 August, 2004) "Critical Data Availability in Real time" Retrieved at http://www.trescon.com.br/trescon.com.br/news/2/Comdex%20Brasil%20August%202004%20Tutorial.pdf. Accessed 4 October, 2005
Mimer 8, Product Overview" Retrieved at http://developer.mimer.com/documentation/pdf_81/prodov_81.pdf. Accessed 4 October, 2005
Norvag, Kjetil; Bratbergsengen, Kjell. "Write Optimized Object Oriented Database Systems"
Retrieved at http://www.idi.ntnu.no/grupper/db/research/tech_papers/SCCC97_writeopt/sccc97.pdf. Accessed 5 October, 2005
Resilience" Retrieved at http://developer.mimer.com/documentation/html_82/Mimer_SQL_Technical_Description/24%20_7%20Operation2.html. Accessed 4 October, 2005
Shadow Files" Retrieved at http://www.cvalde.net/features/f4/ShadowFiles.htm. Accessed 4 October, 2005
Welcome, a Cautionary Tale" (July, 2004) Vol: 7. Retrieved at http://www.imagingsolutions.com/pdf/July%202004%20newsletter%20-%20Disaster%20Recovery.pdf. Accessed 4 October, 2005
