What is ASM and it's Architecture in Oracle 11g r2

Overview

• This features come since last oracle 10g.
• The first foll ASM (Automatic Storage Management ) is one power-full tool that will help to oracle database file storage management into disk or tap drive. 
• The ASM is really cool way to store database file, it's one of many feature of oracle that me-makes oracle database the premier relational database management system.

   

Description  

• The ASM installed as a separate instance as part of gird infrastructure [ RAC / Standalone ] environment.
• It don't including data-file, data-dictionary but it can read PASSWORD file.
• If you want to connect with ASM instance then super user privilege is required [ SYSASM]  and it use PASSWORD file for authenticate.
• If you want to access this functionality you must create ASM instance before your database start.
• You can create your ASM instance through ASMCA [ Automatic Storage Management Configuration Assistant ] or DBCA [ Database Configuration Assistant ]. 

  

  Create ASM Disk Group

• ASM use a disk group for storing data files and ASM also uses the OMF [ Oracle Managed Files ] feature to simplify database file management.
• Some benefit  as below 
• Mirroring     It increase availability of database doing copy to one or more destination.
• Striping        It spread data evenly across all the disk in same disk group.

Architecture

    

ASM INSTANCE ARCH.

 

• Memory Areas
1. Shared Pool       The shared pool contains shared cursors, control structures,stored procedures and other structures  and you can set it's value using SHARED_POOL_SIZE = integer [K | M | G]. And do this query in  ALTER SYSTEM Command.
2. Large Pool          It is used for parallel query performance, RMAN recovery and bakcup and you can set it's value using LARGE_POOL_SIZE = integer [K | M | G]. And do this query in  ALTER SYSTEM Command.
3. ASM Cache        It is used for ASM instance and ASM and it is automatically manage.
4. Free Memory      It contain free [ unused ] space when will be come a burden on any cache or pool then it will decrees it's size.

• Background Processes 
1. RBAL     It is a coordinates re-balance activity for disk group and no of processes are RBAL0, RBAL1,...
2. ARBn      It re-balance data extends within an ASM disk group, and in there are ARB0 - ARB9  and ARBA are process.
3. GMON    It monitor all mounted ASM disk groups.
4. Onnn        It maintain a connection to ASM instance for metadata operation.
5. PZ9n        One or more parallel slave process used in fetching data on cluster ASM installation fro GV$ views. 
6. MARK     It is used for set HWM [ High Water Mark ] it set on the disk's segment. This essentially tracks which extents require resync for offline disks

    

• Connectivity with database instance and ASM instance in standalone database and RAC database.
• In RAC environment the asm as well as db instance will work together and also this environment has more then two instance have.

Connectivity between ASM inst. and DB inst.  [standalone env.]