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Oracle Performance Tuning and Optimization
(Publisher: Macmillan Computer Publishing)
Author(s): Edward Whalen
ISBN: 067230886x
Publication Date: 04/01/96

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Enhancements

You can make some additional enhancements to improve the performance of the system used for financial applications:

  Block size. Unlike an OLTP system, the financial system can benefit from a larger block size because of the reporting activity and the larger size of the system. I recommend trying a block size of 4,096 or 8,192.
  Clusters. Depending on the application, you may or may not benefit from clusters. The benefit you receive depends purely on the data access patterns and your application.
  Hash clusters. Financial systems typically use tables that are accessed by some sort of ID, such as an account ID. If this is the case in your financial application, you can enhance performance by creating hash clusters on some of those tables. However, if this same data is updated continually or additions are frequently made, hash clusters may result in some performance loss.
  Indexes. Depending on how the data is accessed, you may see significant performance benefits from indexes.
  Multiblock reads and writes. Because financial systems do some reporting and large queries, multiblock reads can be beneficial. The size of the I/Os used in multiblock reads should be 64K.
  Parallel Query option. The Oracle Parallel Query option may offer some benefits for reports or queries of long duration. I recommend using the Parallel Query option.
  Parallel Server option. In this type of environment, you may be able to take advantage of the Parallel Server option. How well it performs depends on how your system is designed and how the users are segmented.

Many of these enhancements can help your performance. The specific effect on your system will vary, but this information works well in most cases.

Review of the Financial System

As you have seen, the financial system has characteristics of both an OLTP and a DSS system. By taking both of these characteristics into account and looking at the data access patterns, you can design the system to work optimally for both environments. Of course, you must make some compromises to accommodate both system types, but these may be minor.

The financial system must be concerned with the user response times as well as the load of large batch mode jobs. In most cases, the system should be built to favor the online users. The larger jobs can usually be deferred until off-peak hours or run at a lower priority to accommodate other users in the system.

These systems are used for mission-critical activities, running the financial activities of many of the world’s largest companies. As a robust and secure RDBMS system, Oracle is well suited for this task.

Replicated Systems

With the introduction of Oracle version 7.0, the RDBMS has facilities for replicating data among servers. There are three ways Oracle provides for replication:

  Read-only snapshots. Data is duplicated on a read-only basis. The data is taken periodically from a master database and copied as a snapshot.
  Updatable snapshot. An updatable snapshot is also a snapshot of master database but may be updated.
  Symmetric replication facility. This facility allows multiple copies of a database to be independently updated and kept in sync. (The symmetric replication facility has been available since Oracle version 7.2.)

These replication techniques have many common characteristics and some unique ones. By studying the characteristics, you can derive some useful tuning tips.

Replicated systems can most effectively be used to provide local access to data, eliminating network traffic. By providing the data locally, you can not only eliminate the time spend waiting for data from a remote system, you can also continue to access the data even when the link has been temporarily disabled.

The type of replication you use depends on your particular needs. If you access the data in a read-only fashion, it is much more efficient to use read-only snapshots. If the data must be kept in sync, you may want to use the symmetric replication facility. The amount of overhead associated with replication increases with the amount of update activity. It is up to you to determine what kind of replication, if any, is right for your installation.

You can also use replication to provide a backup server mechanism. By replicating a system to another server, the replicated server can be used as a backup in case the primary server fails totally.

System Characteristics

The characteristics of a replicated system vary. In addition to considering the types of transactions being performed on the system, you must also consider the replication overhead. The replication overhead has these characteristics:

  Moderate to heavy network usage. Depending on the frequency and amount of replicated data that must be transmitted, the network activity may be significant.
  Update activity. The replicated data is always in the form of an update. It is not necessary to transmit data that has not changed.
  Batch jobs. The replication updates are processed as batch jobs. The amount and frequency depends on the system load.

Replication adds some overhead to a system. If you use or intend to use replication, you should design some additional CPU and I/O capacity into the system.

When designing a replicated system, take care to ensure that sufficient capacity is available in the network. If necessary, add network segments to provide more capacity for the replication facility.


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