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. Notice that all the ASM processes begin with asm, whereas the RDBMS instance processes begin with ora.

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

ps –ef|grep asm
oracle 7186 1 0 May30 ? 00:00:13 asm_pmon_+ASM1
oracle 7188 1 0 May30 ? 00:00:01 asm_vktm_+ASM1
oracle 7192 1 0 May30 ? 00:00:02 asm_diag_+ASM1
oracle 7194 1 0 May30 ? 00:00:41 asm_ping_+ASM1
oracle 7196 1 0 May30 ? 00:00:00 asm_psp0_+ASM1
oracle 7200 1 0 May30 ? 00:02:44 asm_dia0_+ASM1
oracle 7202 1 0 May30 ? 00:01:42 asm_lmon_+ASM1
oracle 7204 1 0 May30 ? 00:06:36 asm_lmd0_+ASM1
oracle 7206 1 0 May30 ? 00:04:36 asm_lms0_+ASM1
oracle 7210 1 0 May30 ? 00:00:00 asm_mman_+ASM1
oracle 7212 1 0 May30 ? 00:00:01 asm_dbw0_+ASM1
oracle 7214 1 0 May30 ? 00:00:01 asm_lgwr_+ASM1
oracle 7216 1 0 May30 ? 00:00:02 asm_ckpt_+ASM1
oracle 7218 1 0 May30 ? 00:00:00 asm_smon_+ASM1
oracle 7220 1 0 May30 ? 00:12:46 asm_rbal_+ASM1
oracle 7222 1 0 May30 ? 00:00:43 asm_gmon_+ASM1
oracle 7232 1 0 May30 ? 00:00:04 asm_lck0_+ASM1
oracle 7444 1 0 May30 ? 00:10:04 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 – ASM Bridge: 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 offlined disk is onlined.

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.

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