Oracle Database Background Processes Cheat Sheet
General Background Processes.
| Acronym | Process Name | Description |
| SMON | System Monitor Process | Performs recovery after instance failure and monitors temporary segments and extents. |
| PMON | Process Monitor | Recovers failed process resources. If Shared Server architecture is used, PMON monitors and restarts any failed dispatcher or server processes. |
| LGWR | Log Writer Process | Writes the log buffer out to the redo logs. |
| DBWn | Database Writer Process | Writes dirty buffers from the buffer cache to the data files. Possible processes include DBW0–DBW9 and DBWa–DBWz |
| CKPT | Checkpoint Process | Writes checkpoint information to control files and data file headers. |
| ARCn | Archiver Process | Writes filled redo logs to the archive log location(s). Possible processes include ARC0–ARC9 and ARCa–ARCt. |
| DIA0 | Diagnostic Process | Responsible for hang detection and deadlock resolution. Triggers DIAG to perform diagnostic tasks. |
| CJQ0 | Job Queue Coordinator Process | Spawns slave processes (Jnnn) to execute jobs in the queue |
| MMAN | Memory Manager Process | Serves as the SGA Memory Broker and coordinates the sizing of the memory components |
| MMNL | Manageability Monitor Lite Process | Performs frequent and lightweight manageability related tasks, such as session history, capture and metrics computation. |
| MMON | Manageability Monitor Process | Collects statistics for the Automatic Workload Repository. |
| RECO | Recoverer Process | Resolves failures involving distributed transactions. |
Advanced Queuing Background Processes
| Acronym | Process Name | Description |
| Qnnn | AQ Server Class Process | Processes messaged in the Streams AQ queue. Spawned by QMNC. |
| QMNC | AQ Coordinator Process | Monitors message queues. Spawns Qnnn Processes |
Automatic Storage Management Background Processes
| Acronym | Process Name | Description |
| ARBn | ASM Rebalance
Process |
Rebalances data extents across the ASM file systems. Possible processes are ARB0 – ARB9 and ARBA. |
| ASMB | ASM Background Process | Communicates with the Automatic Storage Management instance. |
| DSKM | Slave Diskmon Process | Acts as conduit between RDBMS and ASM instances and the Master Diskmon daemon to communicate I/O Fencing Information, I/O Resource Manager Plans, and Transaction Commit Cache information to SAGE storage. If no SAGE storage is used, the slave diskmon process will exit silently after startup of the instance. |
| GMON | ASM Disk Group Monitor Process | Maintains disk membership in ASM disk groups. |
| MARK | Mark AU for Resynchronization Coordinator Process | Marks ASM Allocation Units as stale following a missed write to an offline disk. |
| RBAL | ASM Rebalance
Master Process |
Coordinates rebalance activity for disk groups in an Automatic Storage Management instance. Performs global opens on Automatic Storage Management disks. |
| DRnn | ASM Disk
Resynchronization Slave Process |
Resynchronizes the contents of an offline disk. When a disk online SQL command is issued on a disk or disks that are offline, ASM spawns DRnn. Depending on the load, more than one slave may be spawned. |
Data Guard Background Processes
| Acronym | Process Name | Description |
| MRP0 | Managed Standby Recovery Process | coordinates the read and apply process of redo in a physical standby database.
|
| RFS
|
Remote File Server
|
is responsible for receiving the redo data, which is sent by the primary database to the standby database |
| LSP0 | Logical Standby Coordinator Process | Assigns transactions to different Data Guard appliers and coordinates among them to ensure that dependencies between transactions are honored. |
| LSP1 | Logical Standby Dictionary Build Process | Builds the data dictionary for the Logical Standby. |
| LSP2 | Logical Standby Set Guard Process | Maintains Guard Standby information for the Logical Standby. |
| DMON
|
Data Guard Broker Monitor Process
|
runs on every instance in a Data Guard broker configuration. It communicates with local database and DMON processes of the remote databases. The broker-related requests and the monitoring information are transferred on this communication channel.
|
|
FSFP
|
Data Guard broker fast-start failover pinger process
|
is used for the management of fast-start failover status
|
| RSM0 | Data Guard Broker
Worker Process |
Used by the DMON process to manage and
monitor the database. |
Real Application Clusters Background Processes
| Acronym | Process Name | Description |
| ACMS | Atomic Control File to Memory Server Process | Contributes to ensuring a distributed SGA memory update is either globally omitted on success or globally aborted in the event of a failure in an Oracle RAC environment. |
| GTXn | Global Transaction Process | Provides transparent support for XA global transactions in an Oracle RAC environment. The database auto tunes the number of these process based on the workload of XA global transactions. Possible processes are GTX0–GTX9 and GTXa– GTXj |
| LCK0 | Instance Enqueue Background Process | Manage the global enqueued requests and the cross-instance broadcast. Handles all requests for resources other than data blocks. |
| LMD0 | Global Enqueue Service Daemon 0 Process | Manages enqueue manager service requests for Global Cache Service enqueues to control access to global enqueues and resources. The LMD0 process also handles deadlock detection and remote enqueued requests. Remote resource requests are the requests originating from another instance. |
| LMON | Global Enqueue Service Monitor Process | Monitors the entire cluster to manage the global enqueues and the resources. Manages instance and process failures and the associated recovery for the Global Cache Service (GCS) and Global Enqueue Service (GES). In particular LMON handles the part of recovery associated with global resources. LMON-provided services are also known as cluster group services (CGS). |
| LMSn | Global Cache Service Process | Handles remote Global Cache Service (GCS) messages. The number of LMS processes varies depending on the amount of messaging traffic among nodes in the cluster. |
| PING | Interconnect Latency Measurement Process | Assesses the latencies associated with communications for each pair of instances. Every few seconds, the process in one instance (INSTANCE_NUMBER value) sends two messages to each instance (TARGET_INSTANCE value). One message has a size of 500 bytes and the other has a size of 8 KB. The message is received by the PING process on the target instance and is immediately acknowledged. The time for the round-trip is measured and collected. |
| RMSn | Oracle RAC Management Process | Performs manageability tasks for Oracle RAC, such as creation of RAC-related resources when new instances are added to the clusters. |
| RSMN | Remote Slave Monitor Process | Manages background slave process creation and communication on remote instances. |
Source : Oracle Documentation
