what is VSS Writer in Oracle ??

We often see the VSS services in Window  Server . It seems that this service has nothing to do with window because it is created by Oracle but not such .I have tried to cover topic and mention few links which will help us to understand this topic. 

What is VSS ?

VSS is an infrastructure on Windows server platforms that enables applications to create shadow copies. A shadow copy is a consistent snapshot of the data held on a volume or component at a well-defined point in time.  VSS provides a Windows-specific interface that enables coordination between requestors that back up data, writers that update data on disk, and providers that manage storage . Oracle Database functions as a writer that is integrated with VSS-enabled applications.

We  can  use  VSS-enabled  software  and  storage  systems  on  Windows  to  back   up  and  restore  an Oracle  database. A  key  benefit  is  the  ability to use a VSS-enabled application to make an online backup of the whole database .

How Oracle VSS works for Database Backup and RecoveryOracle ?

VSS  is  installed  automatically wit h file . If   the  database   is   in  ARCHIVELOG  mode , then  an    online  backup  can  be  taken  else only  a  closed  backup is  possible. VSS  is  a  service  on  Windows operating system to create shadow copies. This coordinates the activities of the fundamental   services  of requestors,  providers,  and  writers  in  the  creation  and use of shadow copies. The benefit of  an Oracle VSS service is that it coordinates an Oracle database instance and  other  VSS  services .A VSS  requestor requests VSS service to create  shadow copies.  A VSS provider manages  storage  volumes  and creates shadow copies. A VSS writer writes data to disk. In  a recovery  situation select  the database component and restore it. Later open the database in read  only  mode  with resetlogs option.  To restore few components of the database, select them and restore them  individually.

References :  http://blogs.technet.com/b/josebda/archive/2007/10/10/the-basics-of-the-volume-shadow-copy-service-vss.aspx
http://www.sswug.org/articles/viewarticle.aspx?id=44664




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