Post date: Feb 12, 2019 3:34:3 AM
ASM uses disk groups to store datafiles; an ASM disk group is a collection of disks that ASM manages as a unit. Within a disk group, ASM exposes a file system interface for Oracle database files. The content of files that are stored in a disk group are evenly distributed, or striped, to eliminate hot spots and to provide uniform performance across the disks. The performance is comparable to the performance of raw devices.
ASM file components:
Extents
ASM Striping
File Templates
- Simplifies and automates storage management
- Increases storage utilization and agility
- Delivers predictable performance, availability and scalability.
- Support database failure in the event of server crash.
- Integrated storage management with ACFS
Mirroring protects data integrity by storing copies of data on multiple disks. The disk group type determines the mirroring levels with which Oracle creates files in a disk group.
When you create a disk group, you specify an ASM disk group type based on one of the following three redundancy levels:
Normal for 2-way mirroring
High for 3-way mirroring
External to not use ASM mirroring, such as when you configure hardware RAID for redundancy
Files that are stored in ASM disk groups are called ASM files. Each ASM file is contained within a single ASM disk group. Oracle Database communicates with ASM in terms of files. This is identical to the way Oracle Database uses files on any file system. You can store the following file types in ASM disk groups:
Control files
Datafiles, temporary datafiles, and datafile copies
SPFILEs
Online redo logs, archive logs, and Flashback logs
RMAN backups
Disaster recovery configurations
Change tracking bitmaps
Data Pump dumpsets