Oracle Net8 Administrator's Guide Release 8.0 A58230-01 |
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# 3
Planning Your Network

Net8 provides a variety of options to help you design and manage networks that are both flexible and easy to use. With Net8's enhanced scalability and manageability features, you can develop a network to support a wide range of environments whether they be simple workgroups or large mission critical enterprises.

This chapter describes considerations for planning a network using Net8. It explains the relationships of the network products, and options for expanding and better managing your future network. It includes the following sections:

- Section 3.1, "Planning Overview"
- Section 3.2, "Defining Your Network Layout"
- Section 3.3, "Resolving Service Names"
- Section 3.4, "Improving Large Network Performance"
- Section 3.5, "Planning Summary"

## 3.1 Planning Overview

Take the time to review and plan your network before you configure it. As you are planning your Oracle network, remember to keep future needs in mind as well as present requirements. Some of the more important decisions which you will need to make regarding your network include:

- Defining your network layout
- Resolving service names
- Managing connection requests
- Improving network performance

## 3.2 Defining Your Network Layout

The following checklist is provided to help you outline the main components of your network.

1. Define from the outset what it is you hope to accomplish with your network.
2. Research the functionality required by your client applications, then assess the resources that are available to meet those requirements.
3. Determine which machines or nodes are best suited for client or server applications.
4. Select a networking protocol which best suits your existing or future networking requirements. You may be able to choose a single transport level protocol that works well on all the components in your network. Protocol adapters are available for most of the major protocols on many platforms. Your network may also involve clients or servers operating over more than one protocol.
5. If you decide to use multiple protocols on your network, determine which nodes are best suited to install Oracle Connection Manager. Your choice of nodes will be determined by the networking protocols you have chosen as well as the machine's capacity to handle anticipated traffic.

It helps sometimes to draw a picture of your network layout displaying the logical as well as physical relationships between networking components.

## 3.3 Resolving Service Names

Once you have defined your network layout, you will need to decide how best to configure and manage your network implementation. One of the first and most important decisions that you will need to make is choosing a naming method.

### 3.3.1 Naming Methods

Naming refers to the method used by a client application to resolve a service name to a network address when attempting to connect to a database service. Net8 provides four naming methods:

- Host Naming
- Local Naming
- Centralized Naming using Oracle Names
- External Naming

Depending on the size and characteristics of your network, each method will have positive and negative implications for both how the network is configured and administered.

### 3.3.2 Host Naming

Host naming is a new feature enabling users in a TCP/IP environment to resolve Oracle service names using their existing name resolution service. This name resolution service might be DNS, NIS, or simply a centrally-maintained set of "/etc/hosts" files.

Host naming allows users to connect to an Oracle server simply by using the server computer's host name or host name alias. No client configuration is required to take advantage of this feature. The connection is established by using the default TCP/IP port for the listener, that is, port 1521. Multiple databases per node and database location transparency are supported through matching listener global database names with host name aliases.

Host Naming can eliminate the need for a local naming configuration file (TNSNAMES.ORA) in environments where simple database connectivity is desired. It is not however, suitable for large, complex environments where advanced features such as connection pooling, heterogeneous services or application failover (which require additional connect information) are desired.

#### 3.3.2.1 Establishing a Connection Using the Host Naming Option

The process for establishing a client session using the host naming option is as follows:

1. The client initiates a connect request providing a service name which is also a TCP/IP hostname, or hostname alias.
2. A host naming adapter resolves this service name by generating a network address using the service name as both the TCP/IP hostname and the global database name. The TCP/IP port defaults to 1521.
3. Net8 makes the connect request to the address created.
4. A network listener, listening at registered TCP/IP port 1521, receives the request and establishes a connection to the database with a matching global database name as specified in the listener's configuration.
5. The connection is accepted by the server.

#### 3.3.2.2 Host Naming Zero Configuration Scenario

The host naming option enables clients to connect to a remote server without configuration.

As the Oracle8 server is installed, a listener configuration file is generated automatically. The listener will be configured to support an initial database sharing the same name as the host, using the default TCP/IP listening address. Since host naming is used as a naming method by default, it will be used in the absence of a local naming configuration file and Names Server. Clients can make a connection to the initial database by using the host name as a service name.

Furthermore, clients can make connections to additional instances on the same host if they are aliased properly in an IP address translation mechanism such as DNS, NIS, or a centrally maintained TCP/IP hosts file.

##### 3.3.2.2.1 Host Naming Limitations

Automatic configuration of the listener however, depends upon whether it receives accurate information about the host and domain name for the machine the server is installed on. If you cannot make a connection to the initial database using Host Naming over a TCP/IP network, verify that the global database name in the listener configuration file specifies a complete name, including domain name. For more information on configuring a listener, refer to Section 4.2, "Configuring the Network Listener".

### 3.3.3 Local Naming

Local naming refers to the method of resolving a service name to a network address by using information configured on each individual client. Much like an address book, this information is entered in a local naming configuration file called TNSNAMES.ORA.

#### 3.3.3.1 Establishing a Connection Using the Local Naming Option

The process for establishing a client session using the local naming option is as follows:

1. The client initiates a connect request providing a service name.
2. The service name is resolved to a network address configured in a local naming file.
3. Net8 makes the connect request to the address provided.
4. A network listener receives the request and directs it to the database it is servicing.
5. The connection is accepted by the server.

#### 3.3.3.2 Configuring Local Naming

To configure local naming, proceed as follows:

1. Verify that "TNSNAMES" is listed in the field of selected naming methods in the client profile. If it is not, use the Oracle Net8 Assistant to edit the profile.
2. Verify that service names are correctly mapped to their appropriate network addresses in a local naming configuration file (TNSNAMES.ORA). If they are not, you may use the Oracle Net8 Assistant to add or modify service names. For more information on configuring a local naming configuration file, refer to Section 5.4, "Configuring Service Names Using the Oracle Net8 Assistant".

For information on configuring clients to use the local naming option, refer to Section 5.2.1, "Configuring Naming Methods".

### 3.3.4 Centralized Naming using Oracle Names

Centralized Naming refers to the method of resolving a service name to a network address by using Oracle Names. Oracle Names uses Names Servers to store the names and addresses of all database services on a network. Much like people calling for directory assistance, clients wishing to connect to a server direct their connect requests to a Names Server. Names Servers resolve the service name to a network address and return that information to the client.

#### 3.3.4.1 Establishing a Connection Using the Centralized Naming Option

The process for establishing a client session using the centralized naming option is as follows:

1. The client initiates a connect request providing a service name.
2. The connect request is forwarded to a Names Server where the service name is resolved to a network address. This address is returned to the client.
3. Net8 makes the connect request to the address provided.
4. A network listener receives the request and redirects it to the database it is servicing.
5. The connection is accepted by the server.

#### 3.3.4.2 Configuring Centralized Naming

To configure centralized naming, proceed as follows:

1. Verify that "ONAMES" is listed in the field of selected naming methods in your profile. If it is not, use the Oracle Net8 Assistant to edit the profile.
2. Verify that a Names Server exists and is running on the network. If there are no Names Servers in your network, you may use the Oracle Net8 Assistant to start and configure a Names Server.

For information on configuring clients to use centralized naming using Oracle Names, refer to Section 5.2.1, "Configuring Naming Methods".

For more information on configuring clients to use Oracle Names, refer to Section 5.5, "Configuring Clients to Use Oracle Names".

For additional information on configuring Oracle Names, refer to Chapter 6, "Oracle Names".

### 3.3.5 External Naming

External Naming refers to the method of resolving a service name to a network address by using a supported non-Oracle naming service. Oracle Native Naming Adapters resolve service names stored in customers' native (non-Oracle) naming services. They include:

- Network Information Service (NIS)
- NetWare Directory Service (NDS)

  Note: In previous releases of SQL*Net, these Native Naming Adapters were part of the Oracle Advanced Networking Option. They are now included as a standard part of Net8. Distributed Computing Environment Cell Directory Service (CDS) continues to be available as part of the DCE Integration part of Oracle Advanced Networking Option.

#### 3.3.5.1 Establishing a Connection Using the External Naming Option

The process for establishing a client session using the external naming option is as follows:

1. The client initiates a connect request providing a service name.
2. A native naming adapter forwards the request to a native naming system that resolves the service name to a network address. The address is returned to the client.
3. Net8 makes the connect request to the address provided.
4. A network listener receives the request and redirects it to the database it is servicing.
5. The connection is accepted by the server.

#### 3.3.5.2 Configuring External Naming

To configure external naming using the Oracle Net8 Assistant, proceed as follows:

1. Verify that the applicable Native Naming Adapter has been installed on the client node.
2. Specify the use of an external naming adapter (for example, CDS, NDS, or NIS) in your profile. If it is not, use the Oracle Net8 Assistant to edit the client profile.

For more information on configuring clients to use the external naming option, refer to Section 5.2.1, "Configuring Naming Methods".

#### 3.3.5.3 Oracle Names and Native Naming Adapters

Oracle Names can be used in conjunction with other proprietary or open naming services to provide cross-environment name resolution. For example, Oracle Native Naming Adapters for CDS/DCE, NIS or NDS could be installed on all clients and servers in an enterprise network already running Oracle Names to provide name resolution across multiple name services.

Since Oracle Names is a proprietary name service storing and resolving names and addresses for Oracle databases only, one names solution could be to store all your Oracle services in Oracle Names, and use a directory service such as DNS or X.500 as your global naming service.

### 3.3.6 Choosing a Naming Method

Table 3-1 summarizes the relative advantages and disadvantages of each naming method and provides recommendations for using them in your network.

##### Table 3-1 Naming Method Comparison

Naming Method | Advantages/Disadvantages | Recommended for:
--- | --- | ---
Host Naming | Requires minimal user configuration. The user may provide only the name of the host to establish a connection. Eliminates the need to create and maintain a local names configuration file (TNSNAMES.ORA). Eliminates the need to understand Oracle Names administration procedures. Disadvantages: Available only if all of the following are true: Your client and server are connecting using TCP/IP. The hostname is resolved through an IP address translation mechanism such as Domain Name Services (DNS), Network Information Services (NIS), or a centrally maintained TCP/IP hosts file. No Oracle Connection Manager features are requested. The global database name matches the name the name of the host machine; or the host name is aliased to the database services on the host. | Simple TCP/IP networks (with 10-20 databases) that meet the criteria listed.
Local Naming | Provides a relatively straightforward method for resolving service name addresses. Resolves service names across networks running different protocols. Disadvantages: Requires local configuration of all service name and address changes. | Simple distributed networks with a small number of services that change infrequently.
Centralized Naming | Centralizes network names and addresses in a single place, facilitating administration of name changes and updates. For example, whenever a change is made to an existing server or a new server is added to the network, the change is made only once on one Names Server. This eliminates the need for an administrator to make changes to what potentially could be hundreds or even thousands of clients. Resolves service names across networks running different protocols Disadvantages: Oracle Names stores network names and addresses for Oracle services only. Requires additional setup and administration of Names Servers. | Large, complex networks (over 20 databases) that change on a frequent basis.
External Naming | Allows administrators to load Oracle service names into their native name service using tools and utilities with which they are already familiar. | Networks with existing name services.

## 3.4 Improving Large Network Performance

You may improve the performance of large networks by implementing one of the following:

- "Managing Connection Requests"
- "Connection Pooling"
- "Connection Concentration"
- "Optimizing Data Transfer by Adjusting the Session Data Unit (SDU) Size"
- "Persistent Buffer Flushing for TCP/IP"
- "Configuring Listener Queuesize"

### 3.4.1 Managing Connection Requests

If you expect your network to receive excessive connection traffic, you can use the network listener to manage these requests by redirecting them to either prestarted or prespawned dedicated server processes or dispatcher server processes.

Table 3-2 summarizes the relative advantages of each process and provides recommendations for using them in your network.

##### Table 3-2 Existing Server Processes

Process | Advantages | Recommended for:
--- | --- | ---
Prestarted or prespawned dedicated server processes | Reduces connect time by eliminating the need to create a dedicated server process for each new connection request. Provides better use of allocated memory and system resources by recycling server processes for use by other connections without having to shut down and recreate a server. | Networks where the Oracle shared or multi-threaded server is not supported, or where the creation of a new server process is slow and resource-intensive.
Shared or dispatcher server processes | Utilizes network resources more efficiently than a dedicated server process, thus increasing the throughput and performance of your sessions. Enables you to minimize the memory and processing resources needed on the server side as the number of sessions to the database increases. | Networks where the Oracle shared or multi-threaded server is supported, or where the creation of a new server process is slow and resource-intensive.

For more information on configuring your network listener to redirect connect requests to either prestarted or prespawned dedicated server processes, refer to Section 4.2.3.4, "Configuring Prestarted or Prespawned Dedicated Server Processes".

### 3.4.2 Connection Pooling

Connection pooling is a resource utilization feature that allows you to maximize the number of physical network connections to a multi-threaded server. This is achieved by sharing or pooling a dispatcher's set of connections among multiple client processes. Figure 3-1 shows how connection pooling works.

#### Figure 3-1 Connection Pooling

By using a time-out mechanism to temporarily release transport connections that have been idle for a specified period of time, connection pooling makes these physical connections available for incoming clients, while still maintaining a logical session with the previous idle connection. When the idle client has more work to do, the physical connection is reestablished with the dispatcher.

Connection pooling is enabled by parameters in your server's INIT.ORA configuration file. For more information, refer to the Oracle8 Reference.

### 3.4.3 Connection Concentration

Connection Concentration is a feature that is available through Oracle Connection Manager. It allows you take advantage of Net8's ability to multiplex or funnel multiple client sessions over a single transport to a multi-threaded server. Like connection pooling, concentration optimizes network resources and increases the number of client-server sessions that are possible across a fixed number of physical server ports. Unlike connection pooling, concentration maintains the transport connection.

#### 3.4.3.1 Using Connection Pooling and Concentration

Table 3-3 summarizes the relative advantages with using connection pooling and concentration and provides recommendations for using them in your network.

##### Table 3-3 Connection Pooling and Concentration

Feature | Advantages | Recommended for:
--- | --- | ---
Connection Pooling | Limits the number of network resources used per process. Maximizes the number of client/server sessions over a limited number of physical connections. Optimizes resource utilization. | Networks where many clients run interactive "high think/search time" applications such as messaging and OLAP.
Concentration | Supports large client populations. Allows identification and monitoring of real users. Allows mid-tier applications to support additional services. Requires only a single transport for clients with multiple applications. Requires only a single network connection for database links. | Networks where "continuous" connectivity is required.

### 3.4.4 Load Balancing

Load balancing is a feature that takes advantage of the fact that you can have multiple listeners for a single database or for two or more equivalent databases. By balancing the number of sessions coming into the listeners, you can improve connection performance. This may be achieved in one of two ways:

- Listener load balancing
- Client randomization

#### 3.4.4.1 Listener Load Balancing

The listener load balancing feature allows you to distribute multiple incoming client sessions among several listeners. This feature helps to ensure that no single listener is overburdened. Periodically, each of the service handlers sends its load information to each listener that it is registered with. Thus, each listener knows how busy each of the handlers is and redirects incoming sessions to the least busy of those handlers.

Listener load balancing cannot be used in the following situations:

- Prespawned dedicated server processes cannot use listener load balancing because a prespawned dedicated server process registers itself only with the listener that started it.
- Oracle Parallel Servers have their own method of listener load balancing. For more information, refer to Oracle8 Parallel Server Concepts and Administration.

Listener load balancing is configured by defining multiple listeners for each database. Multiple listeners may exist either on the same platform as the database, or on different nodes as is the case with multi-threaded servers. For more information, refer to the Oracle8 Administrator's Guide.

#### 3.4.4.2 Randomizing Client Requests Among Several Listeners

If more than one listener services a single database, a client will randomly choose between the listeners for its connect requests. This randomization allows all listeners to share the burden of servicing incoming connect requests.

To enable your clients to choose from listeners at random, you will need to configure the different listening addresses for each service name. For more information on configuring service name addresses, refer to Chapter 6, "Oracle Names".

### 3.4.5 Optimizing Data Transfer by Adjusting the Session Data Unit (SDU) Size

Tuning your application to reduce the number of round trips across the network is the best way to improve your network performance. If this is done, it is also possible to optimize data transfer by adjusting the size of the session data unit (SDU).

The SDU is a buffer that Net8 uses to place data before transmitting across the network. Net8 sends the data in the buffer either when requested or when it is full.

Table 3-4 outlines considerations when modifying the size of the SDU may or may not be appropriate.

##### Table 3-4 Considerations for modifying the size of the session data unit (SDU)

Modify session data unit size when: | Do not modify session data unit size when:
--- | ---
The data coming back from the server is fragmented into separate packets You are on a wide area network (WAN) that has long delays Your packet size is consistently the same Large amounts of data are returned | Your application can be tuned to account for the delays You have a higher speed network where the effect of the data transmission is negligible Your requests return small amounts of data from the server

Note:: The SDU size should be set as a multiple of the normal transport frame size. Since the normal Ethernet frame size is 1024, the most efficient SDU size over an Ethernet protocol should be a multiple of 1024, but not more than four times the amount of 1024. If you are using either connection pooling or connection concentration, keep in mind that these features require an additional 16 bytes per transport. For more information on the protocol frame size, refer to your protocol specific documentation.

You may adjust the session data unit size by adding a parameter in your local naming configuration file (TNSNAMES.ORA). For more information, refer to Section 5.4.3, "Configuring Advanced Service Name Options".

### 3.4.6 Persistent Buffer Flushing for TCP/IP

Under certain conditions in some applications using TCP/IP, Net8 packets may not get flushed immediately to the network. Most often, this behavior occurs when large amounts of data are streamed from one end to another. The implementation of TCP/IP itself is the reason for the lack of flushing, and can cause unacceptable delays. To remedy this problem, you can specify no delays in the buffer flushing process. For more information, refer to the section titled, Persistent Buffer Flushing for TCP/IP in Section 4.3.2, "Configuring Persistent Buffer Flushing".

### 3.4.7 Configuring Listener Queuesize

If you anticipate receiving a large number of connection requests for a listening process (such as a network listener, Oracle Connection Manager or Oracle Names) over TCP/IP, Net8 allows you to configure the listening queue to be higher than the system default. For more information, refer to Section 4.2.2.3, "Configuring the Listener to Handle Larger Volumes of Connection Requests".

## 3.5 Planning Summary

Table 3-5 summarizes many of the options you may have chosen as you planned your network.

##### Table 3-5 Network Summary

Subject | Options
--- | ---
Network Layout | Single or Multiple Protocols
Service Name Resolution | Host Naming External Naming Centralized Naming Local Naming
Connection Request Management | Dedicated Server Processes Prestarted/Prespawned Dedicated Server Processes Dispatcher Shared Server Processes
Network Performance | Connection Pooling Connection Concentration Listener Load Balancing Optimizing the Session Data Unit Size Persistent Buffer Flushing Increasing the Listener Queue Size

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