• Arun Kumar

ASM Related Background Process

Oracle ASM instance is built on same Oracle database instance architecture. Most of the ASM background processes are same as the database background process.


In this article, our goal is to find out ASM related background process under both:

  • Database instance and

  • ASM instance


ASM Background Process in DB Instance


Oracle database that uses ASM disks, two new background processes exists

  • RBAL

  • ASMB

ASMB performs communication between the database and the ASM instance. RBAL performs the opening and closing of the disks in the disk groups on behalf of Oracle database.


This RBAL is the same process as in ASM instance but it performs a different function.


To find asm background process in oracle db instance, connect to Oracle database and issue below query


$ sqlplus / as sysdba

SQL> select sid, serial#, process, name, description
from v$session join v$bgprocess using(paddr);

Note the ASMB and RBAL processes in the above list. You can even query using the process id at OS level (ps -ef|grep <process_id>).


ASM Background Process in ASM Instance


Oracle introduced two new background processes first in their 10g version:

  • RBAL

  • ARBn

The RBAL performs rebalancing when a disk is added or removed. The ARBn performs actual extent movement between the disks in the diskgroup.


To find asm background process inside asm instance, connect to ASM instance and issue below query

$ sqlplus / as sysasm

SQL> select sid, serial#, process, name, description
from v$session join v$bgprocess using(paddr);

Please note the ARBn process is started only when there is rebalancing operating happening inside diskgroup.

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