[RAC]ORACLE Database 10g RAC for Administrators學習筆記（一）

0. Introduction

What Is a Cluster?

Interconnected nodes act as a single server

Cluster software hides the structure

Disks are available for read and write by all nodes.

Operating system is the same on each machine

What Is Oracle Real Application Clusters?

Multiple instances accessing the same database

One Instance per node

Physical or logical access to each database file

Software-controlled data access

Why Use RAC

High availability

Scalability

Pay as you grow

Key grid computing features

Levels of Scalability

Hardware: Disk input/output (I/O)

Internode communication: High bandwidth and low latency

Operating system: Number of CPUs

Database management system: Synchronization

Application: Design

Scaleup and Speedup

Global Resources Coordination

RAC使用Global Resource Directory (GRD)來記錄資料庫中資源的使用情況。每個instance管理一部分GRD（resource master）。

Global Cache Services (GCS)-負責在多個instance間維持資料庫的多份copy的一致性。使用Cache Fusion演算法。

Global Enqueue Services (GES)-負責維持instance間除cache fusion外的其他資源並跟蹤enqueue的機制。

Global Cache Coordination: Example

1. The second instance attempting to modify the block submits a request to the GCS.

2. The GCS transmits the request to the holder.

3. The first instance receives the message and sends the block to the second instance. The first instance retains the dirty buffer for recovery purposes (past image).

4. On receipt of the block, the second instance informs the GCS that it holds the block.

Write to Disk Coordination: Example

1. The first instance sends a write request to the GCS.

2. The GCS forwards the request to the holder of the current version of the block.

3. The second instance receives the write request and writes the block to disk.

4. The second instance records the completion of the write operation with the GCS.

5. The GCS orders all past image holders to discard their past images.

Dynamic Reconfiguration

當有節點離開或加入cluster，GRD會重新分配。使用lazy remastering演算法，只重新分配最小部分的GRD。同時，所有instance在GRD的grant情況中把所有對於失敗的instance的引用都去除。

Object Affinity and Dynamic Remastering

Dynamic remastering：GCS會記錄哪些instance經常訪問哪些objects，必要時根據訪問頻度調整GRD的分配。

Global Dynamic Performance Views

GV$檢視-將V$檢視按instance整合的全域性性檢視。

使用特殊的並行機制獲取：coordinator執行在客戶端連線的instance，其他instance上各起一個並行程式。

Additional Memory Requirement for RAC

• Heuristics for scalability cases:

– 15% more shared pool

– 10% more buffer cache

可透過V$RESOURCE_LIMIT中關於ges和gcs的相關統計

Efficient Internode Row-Level Locking

Block的傳輸不受row-level lock的影響

Parallel Execution with RAC

並行執行一般在一個instance上起並行程式，但如有需要也可擴充套件到其他instance上。

RAC Software Principles

Additional background processes

• LMON: Global Enqueue Service Monitor

• LMD0: Global Enqueue Service Daemon

• LMSx: Global Cache Service Processes, where x can range from 0 to j

• LCK0: Lock process

• DIAG: Diagnosability process

Main processes of Oracle Clusterware

• CRSD and RACGIMON: Are engines for high-availability operations

• OCSSD: Provides access to node membership and group services

• EVMD: Scans callout directory and invokes callouts in reactions to detected events

• OPROCD: Is a process monitor for the cluster (not used on Linux and Windows)

RAC Software Storage Principles

CRS_HOME

安裝在本地儲存

ORACLE_HOME

ASM_HOME

可安裝在本地儲存或共享儲存，但在本地儲存上可實現滾動升級

Voting files: Is essentially used by the Cluster Synchronization Services daemon for node-monitoring information across the cluster. Its size is set to around 20 MB.

OCR files: It maintains information about the high-availability components in your cluster, such as the cluster node list, cluster database instance to node mapping, and CRS application resource profiles (such as services, Virtual Interconnect Protocol addresses, and so on). This file is maintained by administrative tools such as SRVCTL. Its size is around 100 MB.

以上兩項在ASM例項起來前就會使用，因此不能存放於ASM儲存，必須是raw device或Cluster File System

Data files

Temp files

Control files

Flash recovery area files

Change tracking file

SPFILE

TDE Wallet

以上必須存放在共享儲存，可以是ASMraw deviceCFS，多個例項公用

Undo tablespace

Online redo log files

以上必須存放在共享儲存，可以是ASMraw deviceCFS，每個例項獨佔

Archive logs

不能存放於raw device，可不存放在共享儲存，但在做recovery時必須使其他例項能訪問（如使用NFS）

Typical Cluster Stack with RAC

Unix和Linux平臺使用UDP on Gigabit Ethernet (GbE) 作為節點間通訊協議

使用Oracle的clusterware可以減少安裝和支援的複雜度，但如使用no-Ethernet的連線或部署了依賴於clusterware的其他應用，則需要安裝vendor clusterware。

RAC and Services

可用service將應用分解成多個邏輯上獨立的系統，更好地進行負載均衡、優先順序控制、效能監控等。（handled by instance using metrics, alerts, scheduler job classes and resource manager.

1. Oracle Clusterware Installation and Configuration

Oracle RAC 10g Installation

– Phase one installs Oracle Clusterware.

– Phase two installs the Oracle Database 10g software with RAC.

Oracle RAC 10g Installation: Outline

1. Complete preinstallation tasks:

– Hardware requirements

– Software requirements

– Environment configuration, kernel parameters, and so on

2. Perform Oracle Clusterware installation.

3. Perform ASM installation.

4. Perform Oracle Database 10g software installation.

5. Install EM agent on cluster nodes.

6. Perform cluster database creation.

7. Complete postinstallation tasks.

Windows and UNIX Installation Differences

• Startup and shutdown services

• Environment variables

• DBA account for database administrators

• Account for running the OUI

Preinstallation Tasks

Check system requirements. 硬體配置、網路配置、共享儲存

Check software requirements. 作業系統版本和相關包、hangcheck-timer Module-Linux必須、安裝OCFS程式包-Linux，可選

Check kernel parameters.核心引數

Create groups and users. 建立使用者和組、放開系統限制、配置遠端cluster安裝（SSH）

Perform cluster setup.

Virtual IP Addresses and RAC

使用虛IP來配置tns服務名-一個接點down時，另一個節點自動接管虛IP，即刻返回錯誤並使客戶端使用其他地址重連，無須等待網路超時時間。

Verifying Cluster Setup with cluvfy

可用於進行一些preinstallation或postinstallation的check

Verifying the Oracle Clusterware Installation

檢查/etc/inittab檔案中是否加如了evmd、cssd、crsd程式的自動啟動

2. RAC Software Installation

3. RAC Database Creation

Database Services

Transparent Application Failover (TAF) policy

• None: Do not use TAF.

• Basic: Establish connections at failover time.

• Pre-connect: Establish one connection to a preferred instance and another connection to a backup instance that you have selected to be available.

Single Instance to RAC Conversion

• Single-instance databases can be converted to RAC using:

– DBCA

– Enterprise Manager

– RCONFIG utility

• Before conversion, ensure that:

– Your hardware and operating system are supported

– Your cluster nodes have access to shared storage

Single-Instance Conversion Using the DBCA

Conversion steps for a single-instance database on nonclustered hardware:

1. Back up the original single-instance database

使用dbca建立模板

檔案路徑可選，預設為$ORACLE_HOME/assistants/dbca/templates/下

選擇“Maintain the file locations”以便於可將檔案restore到當前路徑

生成檔案template_name.dbc（資料庫結構檔案）& template_name.dfb（資料庫映象檔案）

2. Perform the preinstallation steps.

3. Set up and validate the cluster.

4. Copy the preconfigured database image.

5. Install the Oracle Database 10g software with Real Application Clusters.

選擇dbca template selection->Copy the Preconfigured Database Image

Single-Instance Conversion Using rconfig

1. Edit the ConvertToRAC.xml file located in the

$ORACLE_HOME/assistants/rconfig/sampleXMLs directory.

2. Modify the parameters in the ConvertToRAC.xml file as required for your system.

3. Save the file under a different name.

rconfig my_rac_conversion.xml

Single-Instance Conversion Using Grid Control

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