Shulou(Shulou.com)05/31 Report--

This article mainly explains the concept and principle of RAC. The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn the concept and principle of RAC.

One clusterware composition

OCR,VOTING files; background processes; network elements

1.1 background process

(1) Css is used to monitor heartbeat and provide services to prevent cerebral fissure. Is to monitor the running status of the cluster.

(2) Crs provides "high availability service" for application layer resources (CRS Resource), monitors the running status of CRS Resource, and starts, stops, monitors and Failover these resources.

There are two main types of Crs resources

GSD,ONS,VIP and Listener belong to the Noteapps class

Database,Instance and Service belong to the Database-Related Resource class.

(3) the process of EVMD is responsible for publishing various events (Event) generated by CRS. In addition, the previous communication between the CRS and CSS services is done through the EVMD process.

Two RAC processes

GCS, GES and GRD constitute the core function of RAC: cache fusion

LMSn: responsible for transferring data blocks between instances, and the corresponding service is called GCS (global cache service).

LMD: responsible for coordinating the access order of data blocks among multiple instances to ensure consistent access to data. It is responsible for providing GES (global enqueue service) services.

DIAG: monitor the health status of the instance, and collect diagnostic data and record it to alert.log when there is a running error in the instance

Three RAC files

3.1 log document

Redo thread: each instance has a set of redo log, and this set of redo log is called a redo thread. Each instance in RAC sets the thread parameter, which defaults to 0.

If this parameter is set, a private redo thread equal to the thread is used when the instance is started. If the default value is used, the instance startup chooses to use public redo thread

And the instance will use the redo thread exclusively. In the RAC environment, redo log group is numbered at the entire database level. For example, instance 1 has three log groups: 1Magne2 and 3, then the log group of instance 2 should be numbered from 4.

Thank you for your reading, the above is the content of "the concept and principle of RAC". After the study of this article, I believe you have a deeper understanding of the concept and principle of RAC, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.