This chapter describes automated Storage control (ASM) principles and provides a summary of ASM features. This part offers the following topics:
For a listing of the terms which can be used in the Oracle Database storing Administrator's Guide and their particular definitions, reference the Glossary in this guide.
Overview of Oracle Automated Storing Control (ASM)
ASM is an amount supervisor and a file system for Oracle database files that supports single-instance Oracle Database and Oracle genuine Application Clusters (Oracle RAC) designs. ASM is Oracle's recommended storage space management option that delivers an alternative to conventional volume managers, file methods, and raw devices.
ASM makes use of disk teams to store datafiles; an ASM disk group is a collection of disks that ASM manages as a product. Within a disk group, ASM exposes a file system program for Oracle database data. The information of data which are stored in a disk group are uniformly distributed, or striped, to remove hot spots and provide uniform performance over the disks. The overall performance is related to the performance of raw products.
You can add or remove disks from a disk team while a database continues to access files from disk team. Whenever you add or remove disks from a disk team, ASM instantly redistributes the file items and eliminates the need for downtime whenever redistributing the content.
The ASM volume supervisor functionality provides versatile server-based mirroring choices. The ASM regular and large redundancy disk groups allow two way and three-way mirroring respectively. You need to use outside redundancy make it possible for a Redundant variety of Inexpensive Disks (RAID) storage space subsystem to do the mirroring security purpose.
ASM in addition utilizes the Oracle Managed Files (OMF) function to simplify database file management. OMF instantly creates files in specified locations. OMF also names files and eliminates them while relinquishing area whenever tablespaces or data tend to be deleted.
ASM lowers the administrative overhead for managing database storage space by consolidating information storage space into a small number of disk teams. This enables one to combine the storage space for several databases also to offer enhanced I/O performance.
ASM data can coexist along with other storage management choices such as for example raw disks and 3rd party file systems. This capacity simplifies the integration of ASM into pre-existing surroundings.
Oracle business management includes a wizard that permits you to move non-ASM database files to ASM. ASM even offers user friendly management interfaces such as for example SQL*Plus, the ASMCMD command-line screen, and Oracle Enterprise Manager.
Comprehending ASM Concepts
This part defines principles when it comes to key ASM components also it contains the following subjects:
About ASM Times
An ASM instance is made on the same technology as an Oracle Database instance. An ASM example features something Global region (SGA) and background processes being just like those of Oracle Database. However, because ASM works fewer jobs than a database, an ASM SGA is significantly smaller than a database SGA. Besides, ASM has actually a minor performance influence on a server. ASM instances mount disk groups to produce ASM data accessible to database cases; ASM cases try not to install databases.
ASM metadata may be the information that ASM makes use of to regulate a disk team plus the metadata resides inside the disk group. ASM metadata includes the next information:
- The disks that participate in a disk group
- The amount of room that can be found in a disk group
- The filenames of this files in a disk group
- The place of disk team datafile information extents
- A redo log that registers information about atomically switching information blocks
ASM and database instances require provided usage of the disks in a disk team. ASM instances handle the metadata regarding the disk group and offer file layout information into the database cases.
ASM instances could be clustered utilizing Oracle Clusterware; there's one ASM example for each group node. If there are several database circumstances for various databases on the same node, then your database cases share equivalent single ASM example thereon node.
If ASM instance on a node fails, then all the database cases thereon node additionally fail. Unlike a file system failure, an ASM example failure doesn't need restarting the os. In an Oracle RAC environment, the ASM and database circumstances on surviving nodes automatically recover from an ASM example failure on a node.
shows one node setup with one ASM instance and several database circumstances. The ASM example handles the metadata and provides area allocation for ASM files. When a database instance creates or starts an ASM file, it communicates those requests toward ASM example. In reaction, the ASM instance provides file extent chart information into database instance.
In, there are 2 disk groups: one disk group features four disks as well as the other has actually two disks. The database can access both disk groups. The setup in programs several database instances, but only one ASM instance is needed to serve the multiple database instances.
shows an ASM group in an Oracle RAC environment in which ASM provides a clustered pool of storage space. There clearly was one ASM example for every node serving several Oracle RAC or single-instance databases when you look at the cluster. The databases tend to be consolidated and sharing equivalent two ASM disk groups.
A clustered storage space pool is shared by several single-instance Oracle Databases as shown in . In this instance, several databases share typical disk teams. A shared ASM storage space pool is attained by utilizing Oracle Clusterware. However, this kind of environments an Oracle RAC license is not needed.
ASM instances being on separate nodes need not participate an ASM group nor talk to one another. However, multiple nodes which are not section of an ASM group cannot share a disk group. To fairly share a disk group among numerous nodes, you have to install Oracle Clusterware on the nodes, whether you install Oracle RAC on the nodes.
About ASM Disk Groups
A disk team consists of multiple disks and it is might item that ASM manages. Each disk group contains the metadata that is required the management of space in the disk group.
Files tend to be allocated from disk groups. Any ASM file is totally contained within just one disk group. But a disk team might contain files belonging to a few databases and an individual database may use data from multiple disk teams. For the majority of installments you'll need only a small amount of disk teams, frequently two, and hardly ever more than three.
Disk group elements consist of disks, files, and allocation devices. shows the connections among ASM disk group elements.