Automatic Storage Management (ASM) is oracle’s logical volume manager, it uses OMF (Oracle Managed Files) to name and locate the database files. It can use raw disks, filesystems or files which can be made to look like disks as long as the device is raw. ASM uses its own database instance to manage the disks, it has its own processes and pfile or spfile, it uses ASM disk groups to manage disks as one logical unit.

The benefits of ASM are

  • Provides automatic load balancing over all the available disks, thus reducing hot spots in the file system
  • Prevents fragmentation of disks, so you don’t need to manually relocate data to tune I/O performance
  • Adding disks is straight forward – ASM automatically performs online disk reorganization when you add or remove storage
  • Uses redundancy features available in intelligent storage arrays
  • The storage system can store all types of database files
  • Using disk group makes configuration easier, as files are placed into disk groups
  • ASM provides stripping and mirroring (fine and coarse gain – see below)
  • ASM and non-ASM oracle files can coexist
  • ASM is free

Following are some of the Whitepapers

1. Filesystems in Oracle database