Oracle RAC knowledge points

Oracle RAC knowledge points

Database Planning should be oriented to business characteristics and needs, rather than RAC for the availability of RAC. In fact, RAC is not omnipotent, and the following knowledge points need to be mastered.

1. Benefits of using RAC

1.1 improve application system performance and Database Transaction processing capability

When the transaction processing capability of a single host resource or single instance database is affected, RAC can greatly improve the concurrency.

The resource usage of the host is not a simple sum. For example, in the RAC environment of two nodes, the CPU usage of each node is 50%. If all resources are transferred to a single node, the CPU usage is not equal to 100%, which may be 70%. Therefore, resource usage is largely due to interaction costs.

When the interaction cost is too high, the processing efficiency will be greatly reduced.

1.2 improve database high availability, especially in the active-active architecture. The benefits are as follows:

There is no need to switch between the local server and the local remote server, achieving extremely stable and predictable failover in seconds.

The back-end data center for business connection is the same-City active-active center. If any site fails, the business will not be affected, which greatly improves the service response capability, it also greatly increases the maintenance and other daily O & M management time.

3. Selection of RAC

Are there many full table scans?

Why is the index competitive?

Is it hard to compete for high water levels?

Why is sequence fierce?

Is the cost of genuine authorization, installation, and O & M within the budget?

4. Side effects of RAC

Resource Competition costs multiply, especially in Load Balancing

The depth of code access becomes deeper, leading to bugs. the overall stability of the database is even worse than that of a single node.

Inconsistent SQL Execution plans between nodes

High failure rate of Heartbeat Network

Differences between versions

High requirements on maintenance personnel skills and experience

If the data block contention in a single instance is severe, it will be a disaster after the data is migrated to RAC, and the performance may deteriorate. In this case, I bought another small machine and only implemented the HA function, but I paid for the performance degradation. Not worth the candle!

When one hang instance is in use, RAC availability is not guaranteed.

5. During Installation

We recommend that you install the latest database patch.

Bind a heartbeat network to a dual-nic

The operating system version of the host must be consistent, and the configuration is best consistent.

Deploy host Resource Monitoring scripts, such as OSW

Perform Various brute force tests, such as CRS/host startup test and network cable plugging test.

Preventive settings of various parameters, such as Oracle's DRM Parameters

 

6. During O & M

The application end adjusts the RAC features. It is recommended that the service be run by node.

A deadlock may occur on multiple nodes.

Do not add data files to a local hard disk.

First shut down the database, then shut down the CRS software, and finally shut down the host

Increase the buffer cache and shared pool size after converting a single machine to RAC.

Exercise caution when enabling parallelism. Do not run the program in parallel across nodes.

Easily ignored database Parameters

7. Several Suggestions for learning RAC

Familiar with basic operations of vmware or Oracle vbox

Installation, upgrade, and repeated installation and upgrade

Read the official documentation, know "what", "How to do it", and check other documents.

Perform the following operations in the lab environment:

CRS Resource Management

Add or delete an ASM disk or a disk group

OCR/voting disk backup, recovery, mirroring, and deletion operations

VIP/public ip/HAIP/private ip change operation

Learn to view CRS log files

Learn to view the gv $ View

Understand the business characteristics, and especially know which table has the highest Access Frequency on which Node

Familiar with CRS log storage location