Configuring Oracle Cluster Synchronization Services (CSS)

Automatic Storage Management (ASM) requires the use of Oracle Cluster Synchronization Services (CSS), and as such, CSS must be configured and running before attempting to use ASM. The CSS service is required to enable synchronization between an ASM instance and the database instances that rely on it for database file storage.

Overview

Automatic Storage Management (ASM) is a feature in Oracle Database 10g/11g that provides the database administrator with a simple storage management interface that is consistent across all server and storage platforms. As a vertically integrated file system and volume manager, purpose-built for Oracle database files, ASM provides the performance of async I/O with the easy management of a file system. ASM provides capability that saves the DBAs time and provides flexibility to manage a dynamic database environment with increased efficiency.

Advantages of ASM?

Disk Addition—Adding a disk becomes very easy. No downtime is required and file extents are redistributed automatically.
I/O Distribution—I/O is spread over all the available disks automatically, without manual intervention, reducing chances of a hot spot.
Stripe Width—Striping can be fine grained as in Redo Log Files (128K for faster transfer rate) and coarse for datafiles (1MB for transfer of a large number of blocks at one time).
Buffering—The ASM filesystem is not buffered, making it direct I/O capable by design.
Kernelized Asynch I/O—There is no special setup necessary to enable kernelized asynchronous I/O, without using raw or third-party filesystems such as Veritas Quick I/O.
Mirroring—Software mirroring can be set up easily, if hardware mirroring is not available.