Capacity Planning, Sizing, and Tuning

When estimating enterprise-wide and regional requirements for directory usage, plan for future needs. Depending on other configuration choices for replication and failover, there could be more than one directory node, each with its own load and capacity requirements. In this case, you must individually size each directory node.

As an enterprise increases its directory usage, more applications rely on Oracle Internet Directory to serve their requests in a timely manner. Ensure that the Oracle Internet Directory installation can live up to the performance and capacity expectations of those applications.

You can influence the capacity and performance of a given Oracle Internet Directory installation in two phases of the deployment process:

• Planning phase

  During this phase, gather the requirements of all directory users and establish a unified performance and capacity requirement. This consists of capacity planning and system sizing.

• Implementation phase

  Once you have the hardware, tune the Oracle Internet Directory software stack for best use of the hardware resources. This improves the performance of Oracle Internet Directory and of the LDAP client applications.

This section contains these topics:

• Capacity Planning

• Sizing Considerations

• Tuning Considerations

Capacity Planning

Capacity planning is the process of determining performance and capacity requirements. You base these on typical models of directory usage in the enterprise.

When trying to estimate the required capacity of an Oracle Internet Directory installation, consider:

• The type of LDAP client applications

• The number of users accessing those applications

• The nature of LDAP operations those applications perform

• The number of entries in the DIT

• The type of operations performed against the Oracle directory server

• The number of concurrent connections to the Oracle directory server

• The peak rate at which operations need to be performed by the Oracle directory server

• The average latency of operations required under peak load conditions

While estimating these details, allow room for future increases in directory usage.

Sizing Considerations

Once you have established the fundamental capacity and performance requirements, translate them into system requirements. This is called system sizing. Some of the details to consider in this phase are:

• The type and number of CPUs for the Oracle Internet Directory server computer

• The type and size of disk subsystems for the Oracle Internet Directory server computer

• The amount of memory required for the Oracle Internet Directory server computer

• The type of network used for LDAP messages from the clients

Based on current experience, Table 18-1 indicates the approximate level of CPU power required for various deployment scenarios for Oracle Internet Directory:

Table 18-1  CPU Power for Various Deployment Scenarios

Usage	Active Connections	Num CPUs	SPECint_rate95 baseline	System
Departmental	0-500	2	60 to 200	Compaq AlphaServer 8400 5/300 (300Mhz x 2)
Organization wide	500-2000	4	200 to 350	IBM RS/6000 J50 (200MHz x 4)
Enterprise wide	2000+	4+	350+	Sun Ultra 450 (296 MHz x 4)

The amount of disk space required for an installation of Oracle Internet Directory is directly proportional to the number of entries stored in the DIT. Table 18-2gives the approximate disk space requirements for variously sized DITs.

Table 18-2  Approximate Disk Space Requirements for Variously Sized DITs

Number of Entries in DIT	Disk Requirements
100,000	450MB to 650MB
200,000	850MB to 1.5GB
500,000	2.5GB to 3.5GB
1,000,000	4.5GB to 6.5GB
1,500,000	6.5GB to 10GB
2,000,000	9GB to 13GB

The data in this table makes the following assumptions:

• There are approximately 20 cataloged attributes

• There are approximately 25 attributes for each entry

• The average size of an attribute is approximately 30 bytes

The amount of memory required for Oracle Internet Directory is mostly governed by the amount of database buffer cache that a deployment site desires. Often, the size of the database buffer cache is directly proportional to the number of entries in the DIT. Table 18-3 provides estimates of the memory requirements for various DIT sizes:

Table 18-3  estimates of the Memory Requirements for Various DIT Sizes

Directory Type	Number of Entries	Minimum Memory
Small	Less than 600,000	512MB
Medium	600,000 to 2,000,000	1GB
Large	Greater than 2,000,000	2GB

See Also: Chapter 20, "Capacity Planning for the Directory."

Tuning Considerations

Oracle Corporation recommends that you properly tune Oracle Internet Directory before using it in a production environment. Before tuning, ensure that there are adequate testing mechanisms and sample data in the directory to simulate a real world usage scenario. Perhaps you can use the applications that rely on the directory for testing purposes.

Any tool for testing the performance of Oracle Internet Directory must be able to show:

• The overall throughput it is noticing

• The average latency of operations

In this way, the tool provides a feedback mechanism for determining the effects of tuning and providing direction to the overall tuning effort.

Some of the commonly tuned properties of an Oracle Internet Directory installation include:

• CPU usage

  This is determined, to a large extent, by:

  • The number of Oracle directory servers

  • The number of database connections opened by each server

  On the one hand, too large a number of Oracle directory servers and database connections can cause too much contention for available CPU resources. On the other hand, too small a number of Oracle directory servers and database connections can leave much of the CPU power under-utilized. Consider adjusting these numbers to the appropriate levels based on available CPU resources and the expected peak load.

• Memory usage

  The main consumer of memory in an Oracle Internet Directory installation is the database buffer cache, which is part of the SGA. In some cases, allocating a very large database buffer cache can eliminate much disk I/O for Oracle data files. However, it can also cause paging, which is detrimental to performance. Alternatively, having a small database buffer cache causes too much disk I/O, and that is also detrimental to performance. Tune the memory usage of the system so that all consumers of memory in the system can get physical memory without needing to use paging.

• Disk usage

  Because all of the data served by Oracle Internet Directory resides in database tablespaces, pay attention to any tuning that can increase the I/O throughput. Common techniques for disk tuning include:

  • Balancing tablespaces on different logical and physical drives

  • Striping logical volumes onto multiple physical volumes

  • Distributing disk volumes across multiple I/O controllers

    See Also: Chapter 21, "Tuning Considerations for the Directory" for further details on various tuning tips and techniques