Oracle Real Application Clusters

9.1 Introduction

In the previous chapter we looked at the installation and configuration of a RAC environment. During this process we looked at the creation of a RAC database using DBCA versus the traditional manual method. Script creation continues to have several advantages over the GUI-based DBCA utility provided by Oracle, because the script provides an in-depth view of what happens at each stage of the database creation. This level of detailed information is hidden when the DBCA utility is used. Then we also looked at configuring the instances to be cluster aware.

During these discussions we also looked at database administration and configuration commands that are useful for day-to-day operational functions of a database administrator.

What good is a database and a clustered solution, when the characteristics of the database cannot be observed, analyzed, and tuned to satisfy the requirements of the business that it supports? The interfaces required for the observation, analysis, and tuning of RAC, are provided through the data dictionary views.

A photograph of a landscape provides an illustration of the area or imagination of the photographer from the actual characteristics of the area. Similarly, the data dictionary view provides a user-friendly presentation of the data from its underlying physical tables.

Data dictionary view contains a set of underlying system tables that Oracle maintains. The data dictionary views provide some of the cryptic data that is stored in these tables, in a more clean and optimized manner, to the administrators. These values are analyzed to manage the clustered database.

Data dictionary views are also available in a single stand-alone configuration of Oracle. However, in the case of clustered databases that have multiple instances talking to a common shared database, additional identification such as an instance number helps to identify how each instance is performing relative to the others and which specific instances could potentially be causing the problem, if any. This helps in drilling down the actual area of the problem.

In this chapter, the various data dictionary views that are more commonly required and used in a RAC implementation will be analyzed and discussed. While many of the views are used for basic day-to-day administrational activities, others are used to determine the health of the database. Only the functionalities of these views will be discussed in this chapter. The details of how some of the performance-related views will be used are covered later in Chapter 13 (Performance Tuning).