[RAC] Oracle RAC background process

I. RAC background process

Lmon:lock Monitor Processes is also known as the Global Enqueue service monitor

Monitor the entire cluster condition, maintain the memory structure of GCS monitor abnormal terminated processes and instances when an instance leaves and joins a cluster, the locks and resources are reconfigured to manage global locks and resources to monitor global lock resources, handle deadlocks, and block

Lck:lock Process

The LCK process is primarily used to manage inter-instance resource requests and cross-instance invocation operations, including data dictionary-like access, and processing non-

CACEH Fusion's Chace resource request (e.g. dictionary cache or row cache request) because the LMS process is responsible for the primary lock management feature, each instance has only one lck process

Lmd:lock Monitor Deamon Process

The LMD process primarily manages access to global queues and resources, updates the corresponding queue state, and processes resources from other instances. The current state of each global queue is stored in the corresponding instance shared memory, which indicates that the instance has the appropriate rights to use the resource. There is a special queue in the shared memory of an instance master that records resource requests from other remote instances, and when a resource request is made by the LMD process of the remote instance, the request points to the LMD of the master instance, and when the LMD process of the master instance receives the request, In a special queue in shared memory, monitor if the resource is invalid, if a valid LMD process updates the state of the resource to the column, and notifies the requesting resource that the LMD process can use the resource queue if the resource queue is being used by another instance or is currently invalid. The LMD process notifies the LMD process application that the instance is in use to release the resource, and when the resource release becomes valid, the LMD process of the master instance updates the state of the resource queue and notifies the requesting resource instance of the LMD process that the resource queue can use

Global Queue Service (GES): primarily responsible for maintaining consistency within the dictionary cache and in the library cache. The dictionary cache is a cache of data dictionary information stored in an instance's SGA for high-speed access. Because the dictionary information is stored in memory, modifications to the dictionary (such as DDL) on a node must be propagated immediately to the dictionary cache on all nodes. GES is responsible for dealing with the above situation and eliminating the differences between instances. For the same reason, in order to parse the SQL statements that affect these objects, the library cache locks on the objects in the database are removed. These locks must be maintained between instances, and the global queue service must ensure that there are no deadlocks between multiple instances requesting access to the same object. The Lmon, LCK, and LMD processes work together to implement the functionality of the Global queue service. GES is an important service that adjusts other resources among nodes in a RAC environment, in addition to the maintenance and management of the data block itself (completed by GCS).

Lmsn:lock Monitor Services is also known as GCS (Global Cache Services) processes

The LMS process is primarily used to manage access to databases within the cluster and to transmit block images in the buffer cache of different instances, when on a block of data

When a consistent read occurs, the LMS is responsible for rolling back the data block and copy it to the requested instance on at least 2 LMS processes per RAC node

Global cache Service (GCS): To be combined with cache Fusion to understand that the global cache involves data blocks. The global cache service is responsible for maintaining cache consistency within the global buffer store, ensuring that an instance can obtain a global lock resource at any time when it wants to modify a block of data, thereby avoiding the possibility of another instance modifying the block at the same time. The instance that is being modified will have the current version of the block (both committed and uncommitted) as well as the Block's front image (post image). If the block is also requested by another instance, the global cache service is responsible for tracking the instance that owns the block, what version of the owning block, and what mode the block is in. The LMS process is a key component of the global cache service.

diag:diagnostic Deamon

oracle10g The new background process routinely monitors the health of the instance, while also monitoring whether the instance hangs or the critical diagnostic information in case of a deadlock collection instance and process error This process updates the alert log file and writes some important alarm messages

Second, RAC service process

crs-Cluster resource Service (cluster ready services)

Basic procedures for managing high-availability operations within a cluster CRS manages any transaction known as resource database, instance, listener, virtual IP, application process, etc. CRS is a resource configuration information stored in OCR to manage these resources when a resource's state changes, the CRS process generates an event that includes the start, shutdown, monitoring, and failover, which is managed and initiated by the root user,crsd If a failure causes a system reboot

css-Cluster Sync Service (Cluster Synchronization Service)

managing membership of a cluster node controls which node is the member of the cluster, the node notifies the cluster member when joining or leaving the cluster to control the cluster configuration information, which causes the cluster to restart, provides a heartbeat mechanism to monitor the cluster status (DISK HEARTBEAT and NETWORK Hearbeat), the process is run by Oracle User management

EVMD Incident Management Service (event Management)

The Event Management Daemon publishes a background process for CRS creation events

ons-Event Publishing and subscription services (Oracle Notification service)

Rapid application of Communication notification event publishing and subscription services

ocr-oracle Cluster Register

Cluster registration file, record information about each node the various resource information for the RAC cluster is saved as if the Windows registry is stored on a shared disk, and all instance shares have 2 spare disks by default

voting disk voting disks

The quorum mechanism is used to arbitrate the behavior of multiple nodes to the shared node, to avoid the occurrence of conflicts stored on the shared disk, all instances shared to determine the relationship of each instance when a node fails, the voting disk determines which instance to evict by default 3 disks

Oprocd (Process Monitor Daemon) Detect CPU Hang (non-Linux platform use), cluster process management-process monitor for the cluster. To protect shared data IO fencing

Organize according to Http://blog.sina.com.cn/s/blog_61cd89f60102ef28.html

[RAC] Oracle RAC background process