Appendix B: Overview of Real Application Clusters

This chapter describes how you can use the Enterprise Manager Database Control Cluster Database Home page and the Cluster Database Instance Home page to proactively and reactively configure and manage your database environment. In addition, this tutorial describes how you can view the Cache Coherency metrics for the entire Cluster Database and identify processing trends and optimize performance for your RAC environment.

Topics

This tutorial covers the following topics:

Using the Cluster Database Home Page

Using the Cluster Database Instance Home Page

Using the Cluster Cache Coherency Page

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You are managing an Oracle Real Application Clusters (RAC) database. The cluster consists of two nodes, which are residing within a single Linux Virtual Machine (VM). Two instances are mounted on the RAC database. The database files are stored in shared storage, which is managed by Oracle's Automatic Storage Management (ASM). Oracle Enterprise Manager Database Control automates and simplifies management of the cluster, the RAC database, and its instances.

Why Use RAC

Oracle Real Application Clusters enables high utilization of a cluster of standard, low-cost modular servers such as blades. RAC offers automatic workload management for services. Services are groups or classifications of applications that comprise business components corresponding to application workloads. Services in RAC enable continuous, uninterrupted database operations and provide support for multiple services on multiple instances. You assign services to run on one or more instances, and alternate instances can serve as backup instances. If a primary instance fails, Oracle moves the services from the failed instance to a surviving alternate instance. Oracle also automatically load-balances connections across instances hosting a service.

RAC harnesses the power of multiple low-cost computers to serve as a single large computer for database processing, and provides the only viable alternative to large-scale SMP boxes for all types of applications. RAC, which is based on a shared-disk architecture, can grow and shrink on demand without the need to artificially partition data among the servers of your cluster. RAC also offers a single-button addition and removal of servers to a cluster. Thus, you can easily provide or remove a server to or from the database.

The Cluster Cache Coherency Instances page provides real-time monitoring of global cache statistics. The Cluster Cache Coherency Instances page displays tables of metrics from the following groups for all cluster instances:

Block Access Statistics

Global Cache Convert, Global Cache Current Block Request, Global Cache CR Block Request

Top 5 Library Cache Lock and Top 5 Row Cache Lock

Using the Cluster Database Home Page

The Cluster Database Home page enables you to view the current state of the Real Application Clusters database by displaying a series of metrics that portray its overall health. This page provides a launch point for the performance, administration, and maintenance of the cluster database environment.

Perform the following steps:

1.

Open your browser and enter the following URL:

http://<hostname>:<port>/em

Login as the sys user as SYSDBA.

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2.

After you successfully log in, you see the Cluster Database Home page for your database. The Home page provides the overall picture of your cluster database health and activities.

On the top left corner, you see the name of the cluster database you are connected to. The Home page has the following sections: General, Host CPU, and Active Sessions.

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Scroll down the page to see the Diagnostic Summary, Space Summary, High Availability, Alerts and Related Alerts sections.

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Scroll down to see the Job Activity, Critical Patch Advisories, Instances, and Related Links sections.

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3.

On the top right corner of the page, you see the link to the Setup, Preferences, Help, and Logout pages. By using Setup, you can  manage administrators, notification methods, configuration of patch management, and so on. The Preference link provides access to managing information, preferred credentials, notification schedules, and so on.

The tabs on this page provide easy access to information in different categories, directly linking to details and tasks on performance, administration, and maintenance. By default, you are taken to the Home tab.

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4.

This View Data drop-down list selection enables you to change your data to be manually refreshed or automatically refreshed.

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5.

The General section provides information about the status of the instances in your database (Up or Down), the cluster it is running on, its Oracle Home, its name, and its version. Click the crs Cluster link to see the Cluster Home page.

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6.

The Cluster Home page provides information about the status of the node(s) in the cluster as well as the status of the database(s) in the cluster. Click the Targets tab to see the targets in the cluster.

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7.

The Targets page shows the targets in the cluster.

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Scroll down the page. Notice that your cluster includes an Automatic Storage Management (ASM) instance. The Managing ASM Disk Groups tutorial contains more details about using ASM.

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8.

Click the Interconnects tab to access the Interconnects page. You can use this page to monitor the interconnect interfaces, determine configuration issues, and identify transfer rate-related issues including excess traffic, and so forth.

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9.

Click the Database tab to return to the Cluster Database Home page.

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10.

The High Availability section provides information about your database's ability to recover from instance and media failure. It shows when the last database backup was taken and whether Flashback Logging is enabled.

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11.

The Space Summary section highlights whether there are any tablespaces that have run out of space, or have fragmentation issues.

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12.

The Diagnostic Summary section shows the total number of policy violations and alerts for the database.

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13.

The Alerts section shows all open alerts for the database.

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14.

The Related Alerts section shows alerts for related targets. The Job Activity section provides the statistics of any job activity in the system for the last seven days.

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15.

With Enterprise Manager, you can automate the process of deploying patches to Oracle products within your enterprise, thus reducing the maintenance cost of keeping your software up-to-date. The Critical Patch Advisories section allows you to ensure more timely application of security patches, reducing your exposure to threats.

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16.

The Related Links section provides direct links to different management areas of your cluster database.

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17.

The Instances section provides direct links to the instances of your cluster database. Click the RACDB_RACDB1 instance to access the Cluster Database Instance Home page for the RACDB1 instance.

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Using the Cluster Database Instance Home Page

The Cluster Database Instance Home page enables you to view the current state of the instance by displaying a series of metrics that portray its overall health. This page provides a launch point for the performance, administration, and maintenance of the instance environment.

Perform the following steps:

1.

The Cluster Database Instance Home page provides the overall picture of the instance health and activities. On the top left corner, you see the database instance name.

The top part of the Cluster Database Instance Home page has the following sections: General, Host CPU, Active Sessions, and SQL Response Time.

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Scroll down to view the Diagnostic Summary, Space Summary, High Availability, Alerts, and Related Alerts sections.

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Scroll down again to see the Job Activity and Related Links sections.

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2.

The General section provides information about the status of the instance (Up or Down), where it is running (server and Oracle home), its name, its version, the Oracle net listener, and the ASM instance it uses.

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3.

The Host CPU section provides the overall CPU utilization by the database on the host machine. It also shows the run queue length on the CPU, as well as any paging activity on the host machine.

Active Sessions shows the average number of sessions working (using CPU) or actively waiting during the refresh interval, rounded down to the whole integer. This number is generally less than the total number of sessions connected, as the session idle time is natural and almost always present.

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4.

The High Availability section provides the information about your database's ability to recover from instance and media failure. It shows how much time it will take for your database to recover from instance failure and an overview of database backups. Click the number of seconds related to Instance Recovery Time.

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5.

You see the mean time to recover. This is the estimated recovery time for Oracle to perform Instance Recovery on restart after a Shutdown Abort or an Instance failure. Select the Database Instance: RACDB_RACDB1 locator link.

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6.

Because Instance Recovery Time is a Maintenance task, you are automatically taken to the Maintenance tab. Click the Home tab.

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7.

The Space Summary section shows the percentage of dump area used. The dump area stores dump files created by background and user processes, as well as core dump files. Dump Area Used (%) is an alert threshold that can be edited through the Manage Metrics page.

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8.

The Diagnostic Summary section provides the link to technical advice that Oracle's Automatic Database Diagnostic Monitor (ADDM) tool generates. ADDM is a built-in performance expert that is automatically run every 30 minutes by default. ADDM provides database wide performance diagnostics for both single-instance and Real Application Clusters (RAC) databases. It not only provides "root-cause analysis" but also provides recommendations to help resolve performance problems. Click the Alert Log link.

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9.

There have been a number of ORA- errors recorded in the alert log. Select Last 24 Hours from View Data, and then click Refresh.

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10.

There are no outstanding ORA- errors. Click the Database Instance: RACDB_RACDB1 locator link.

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11.

Click the Database tab to return to the Cluster Database Home page.

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12.

You are now back on the Cluster Database Home page.

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Using the Cluster Cache Coherency Pages

In this section, you learn how to monitor Cache Fusion performance by identifying data blocks and objects which are frequently used by all instances. High concurrency on certain blocks may be identified by Global Cache Service wait events and times. Waiting for blocks to arrive may increase the response time.

The interconnect and internode communication protocols can affect Cache Fusion performance. In addition, the interconnect bandwidth, its latency, and the efficiency of the IPC protocol determine the speed with which Cache Fusion processes block transfers

Perform the following steps:

1.

Click the Performance tab.

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2.

The Performance page appears.

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3.

Scroll to the bottom of the Performance page and click the Cluster Cache Coherency link.

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4.

The Cluster Cache Coherency page appears. Latencies are monitored on this page. Any significant increase in the latency value can be investigated further from this page.

On this page you see the following charts: Global Cache Block Access Latency, Global Cache Block Transfer Rate, and Global Cache Block Transfers and Physical Reads.

Switch to the tabular view by clicking Tabular Format.

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5.

You see the following data categories on the Tabular Format Cluster Cache Coherency page: Global Cache Block Access Latency, Global Cache Block Transfer Rate, and Block Access Statistics.

For each category, you can click on the By Instance link to view a table of metrics for each each instance of the cluster database. Click By Instance for Global Cache Block Transfer Rate.

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6.

This page shows the Global Cache CR blocks received by each instance. This page shows Global Cache statistics for each instance and indicates which instance is generating most of the traffic. Click Database to return to the Cluster Database Home page.

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In this tutorial, you've learned how to:

Navigate the Cluster Home Page
Navigate the Cluster Instance Home Page
View global cache metrics on the Cache Coherency page
Use the metrics to optimize the performance of your RAC environment

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