Volume Shadow Copy Service (VSS) is an infrastructure on Windows server platforms that enables applications to create shadow copies. A shadow copyis a consistent snapshot of the data held on a volume or component at a well-defined point in time.
In other words, this infrastructure enables to create snapshots of separate files or all volume (disk) without an working stop. And it is provided with a kernel of OS Windows.
Oracle service <SID> VSS Writer Serviceis a service of Oracle which provides coordination between a separate copy of Oracle instance (on each copy there is a service) and VSS infrastructure.
It enables, using a third-party software, to do «hot» backup and restore. For example, it is possible to use software solutions Acronis (1567: Creating Backup with Complex Applications Such As Microsoft SQL Server, Oracle or Microsoft Exchange Running on the Server).
All is more detailed it is described in the documentation – 8 Performing Database Backup and Recovery with VSS.
If backup and restore is done without using VSS, it is better to switch-off or generally to delete these services Oracle <SID> VSS Writer Service. Since they consume resources. And also possible memory leak(unpublished Bug:9063341) – Instance Crash Or ORA-04030 Errors When Pagefile Is Full [ID 1358570.1] or Bug 10209909 : ORAVSSW PROCESS CONSUME ALL MEMORY
For control of service it is possible to use oravssw – Installing and Uninstalling the Oracle VSS Writer Service
To delete service:
oravssw <SID> /d