An ASM instance forms and presents is the underlying structure for an ASM dynamic volume.
ASM provides a disk group which is really a logical container for physical space. ASM is very efficient at storing data files but there are many types of files that cannot be stored on ASM and it cannot be read directly by the OS.
In order to expand the functionality of ASM, ADVM was introduced to allow more file types to be stored on ASM managed storage.
ADVM allows you to create a volume on an ASM disk that can be presented to the operating system where a file system (such as ACFS) can be created and that can store most of your database related files as well as other ‘normal’ files that you might wish to place there. The big advantage being that it is backed up by ASM.
Some kernel modules are necessary to provide this service. They are:
- oracleasm – the asm module.
- oracleadvm – the ASM dynamic Volume manager module.
- oracleoks – the kernel services module.
- oracleacfs – the ASM file system module.
You can not use ACFS (Oracle Cluster File Systems) to store:
- Oracle Base Directory.
- Oracle Grid infrastructure home that contains software for Oracle clusterware, ASM, Oracle ACFS or Oracle ADVM components.
- OS root directory
- Boot directory
