Background Processes in Oracle ASM

Once the ASM instance is started, all the basic background processes, as well as some that are specific to the operation of ASM, are started.

On Linux, the ASM processes can be listed using the following command:

ps –ef|grep asm

 asm_pmon_+ASM1
 asm_vktm_+ASM1
 asm_diag_+ASM1
 asm_ping_+ASM1
 asm_psp0_+ASM1
 asm_dia0_+ASM1
 asm_lmon_+ASM1
 asm_lmd0_+ASM1
 asm_lms0_+ASM1
 asm_mman_+ASM1
 asm_dbw0_+ASM1
 asm_lgwr_+ASM1
 asm_ckpt_+ASM1
 asm_smon_+ASM1
 asm_rbal_+ASM1
 asm_gmon_+ASM1
 asm_lck0_+ASM1
 asm_asmb_+ASM1

Some of the more important ASM background processes:

ARBx These are the slave processes that do the rebalance activity (where x is a number).

ASMB - This process is used to provide information to and from the Cluster Synchronization Service (CSS) used by ASM to manage the disk resources. It is also used to update statistics and provide a heartbeat mechanism.

CKPT - The CKPT process manages cross-instance calls (in RAC).

DBWR - This process manages the SGA buffer cache in the ASM instance. DBWR writes out dirty buffers (changed metadata buffers) from the ASM buffer cache to disk.

GMON - This process is responsible for managing the disk-level activities (drop/offline) and advancing diskgroup compatibility.

KATE - The Konductor or ASM Temporary Errands (KATE) process is used to process disks online. This process runs in the ASM instance and is started only when an offline disk is online.

LGWR - The LGWR process maintains the ASM Active Change Directory (ACD) buffers from the ASM instance and flushes ACD change records to disk.

MARK - The Mark Allocation Unit (AU) for Resync Koordinator (MARK) process coordinates the updates to the Staleness Registry when the disks go offline. This process runs in the RDBMS instance and is started only when disks go offline in ASM redundancy diskgroups.

PING - The PING process measures network latency and has the same functionality in RDBMS instances.

PMON - This manages processes and process death in the ASM instance.

PSP0 - This process spawner process is responsible for creating and managing other Oracle processes.

PZ9x - These processes are parallel slave processes (where x is a number), used in fetching data on behalf of GV$ queries.

RBAL - This opens all device files as part of discovery and coordinates the rebalance activity.

SMON - This process is the system monitor and also acts as a liaison to the Cluster Synchronization Services (CSS) process (in Oracle Clusterware) for node monitoring.

VKTM - This process is used to maintain the fast timer and has the same functionality in the RDBMS instances.