Troubleshooting Guide

Overview of Client Connectivity

This section provides an overview of how DB2 clients connect to DB2 servers. This information can help you understand the areas where connectivity problems typically occur.

Client workstations are connected to a DB2 server through a communications protocol (for example, TCP/IP, APPC, Named Pipes (NPIPE), NetBIOS, or IPX/SPX). This connection enables applications to run on a client and interact with DB2. Examples of applications are Lotus Approach, Microsoft Access, or user-written applications.

When an application needs to access a database, it uses a CONNECT statement. The database alias identified in the CONNECT statement references an entry in the client's database directory. This entry contains these important elements:

• The alias name of the database on the server.
• If the database is local, the path where the local database directory resides.
• If the database is remote, the name of a corresponding entry in the node directory. The node directory provides communications information to form the connection.
• The local alias name for the database. The local database alias name and the server database name are usually the same. However, to access databases with the same name that reside on different systems, you must give each database a different local alias name so that your applications can tell them apart.
• When working on DB2 Universal Database Enterprise -- Extended Edition, the catalog node number.

The node directory indicates where the database is physically located. Each node directory entry specifies which network communication protocol to use to connect to the database, and the protocol parameter values required to make the connection.

The database directory and node directory ensure that access to a database is transparent to users and applications, regardless of where the database physically resides. If a database has been cataloged correctly on the client, you can connect to the database if you know the local database alias name.

The catalog node number represents a node as defined within the db2nodes.cfg file, where the CREATE DATABASE statement was issued. All system catalog tables for that database reside on the specified node.

For more information about maintaining the information in the database and node directories, see the Quick Beginnings guide for your platform.

In addition to the directories, the following are required for client communications to a DB2 server:

• Database manager configuration parameters on the server. For example, to determine whether or not DCE directory services is used, the Directory Services Type (dir_type) configuration parameter must be configured. Another example of a configuration parameter is Default Client Communication Protocol (dft_client_comm). This parameter indicates the communication protocols that the client applications on the instance can use for remote connections.
• DB2 registry values. Environment variables are stored in a DB2 registry. Update them with the db2set command. For information on the DB2 registry values available on your operating system, type db2set -lr and press Enter.

  For example, to temporarily override the dft_client_comm configuration parameter, the DB2CLIENTCOMM registry variable can be modified.

• The db2cli.ini and odbc.ini files are ASCII files that store values for DB2 CLI configuration. These files are only needed for CLI or ODBC or JDBC connectivity and not general client connectivity. For more information, see the CLI Guide and Reference.

For details on client connectivity, see the Quick Beginnings guide for your platform.

Client Connectivity Tools

After installing DB2, you can use the following tools to connect a client to a database on a server:

Setup Communications

Sets up communications for server instances, including those that are remote UNIX-based environments. To update communications for a server instance, select the instance in the Control Center and select Setup Communications from the pop-up menu.

Note:

The communications protocol stack must already be set up.

Client Configuration Assistant

Lets you define connections to databases so that the databases can be used by applications.

Alternatively, use the command line processor to set up clients in UNIX-based environments. Refer to the Command Reference for information on the CATALOG DATABASE and CATALOG protocol NODE commands.

For more information, see the Quick Beginnings guide for your platform.