Properties of a direct connection to an ArcSDE geodatabase
Release 9.2 Last modified December 3, 2010	Print all topics in : "Connecting to an ArcSDE geodatabase"

This topic contains the following information:

• A description of a direct connection
  
• When would you use a direct connection?
  
• When wouldn't you use a direct connection?
  
• The direct connect drivers
  
• Database setup files
  
• Required client installations
  
• Client/Database compatibility
  
• Environment variables
  
• Error messages
  
• Direct connections and operating system authentication
  

Connecting directly from a client application to a geodatabase means communication between the database and client takes place via a direct-connect driver not through an ArcSDE service. It also means a lot of the processes that would have taken place on the server are now going to take place on your client machines.

The ArcSDE direct-connect drivers are built from the same software code that is used to build the application server. The difference is the direct-connect drivers are built as dynamically linked libraries and execute in the process space of the client application, whereas the application server (ArcSDE service) is built as an executable program that runs on the server machine.

Since the direct-connect drivers are built from the same software code as the application servers, the same database configuration must be done as when setting up a database to use with the application server. The same ArcSDE administrator and ArcSDE and geodatabase system tables used by the application server configuration must also exist for direct connection configurations. You (or your administrator) must set these up prior to any ArcSDE connection requests. Your client machines must be configured for network access.

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Some examples of when you would use a direct connection

• If you don't want to administer an ArcSDE service
  
The direct-connect database driver doesn't require the administration of the ArcSDE service. There is no intermediate giomgr process to set up, configure, or start.

• The direct connect database driver provides additional options for scaling a system.
  
The direct connect architecture moves the ArcSDE server functionality to the desktop. This removes the ArcSDE load from the database server and will allow additional resources to be freed up for the DBMS, which means you get better scalability on the database server.

• The direct connection configuration can be useful in failover environments.
  
For example, it is easier to configure your system with Oracle Real Application Clusters (RAC) using the direct-connect driver.

• If you want to use operating system authentication for your ArcGIS connections to an ArcSDE for Oracle, DB2, or Informix geodatabase
  
You must use a direct connection to create a spatial database connection using operating system authentication from ArcCatalog to a geodatabase stored in Oracle, DB2, or Informix.

• If you're connecting to an ArcSDE Personal or Workgroup geodatabase
  
You must use a direct connection from ArcGIS Desktop to these geodatabases.

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Some instances for which you would not use a direct connection

• If your desktop machines don't have enough resources to handle the ArcSDE processes
  
• If your ArcSDE geodatabase and your clients are not at the same release
  
To use direct connections, your client applications and ArcSDE must be running the same release. For example, if you have an ArcSDE 9.1 geodatabase, your ArcGIS Desktop and ArcIMS must also be 9.1.

• If you don't want to configure every client machine to make a direct connection
  

More details on the properties of direct connections are below, including a list of things needed or things that you should consider when using a direct connection. (Most apply only to ArcSDE Enterprise geodatabases.) For information on how to configure a client to make a direct connection, see Setting up clients for a direct connection.

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Direct-connect drivers

Direct-connect drivers provide the functionality to connect to and use spatial data in a DBMS. They exist as dynamically linked libraries in the bin directory (Windows operating system) or lib directory (Unix operating system) of your client application.

These drivers are automatically installed for ArcGIS (the whole product suite), ArcView 3.x Database Access, ArcIMS, ArcInfo Workstation, and MapObjects 2. If you are using a custom application built from the ArcSDE C API that is not an ESRI product, you may need to install the direct-connect drivers. You can install the drivers from the ArcSDE Developer Kit CD-ROM located in the ArcSDE media kit. Check with the supplier of your custom application to find out if you need to install these drivers separately.

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Database setup files

You need to install ArcSDE to get the database setup and administration files. If your site only uses direct connections, you do not need to start an ArcSDE service; all you need to do is install the ArcSDE files and follow the postinstallation configuration instructions.

The administration files that get installed with ArcSDE—for example, sdesetup, sdeconfig, and sdedbtune—are useful for managing your database.

The installation DVDs/CDs in the ArcSDE media kit are grouped by platform. To get your database setup files, you will need to install the ArcSDE software specific to your database and platform. For example, if you are using IBM DB2 on a Sun Solaris server, you will select the Sun Solaris DVD or CD from the ArcSDE media kit and install the DB2 version of ArcSDE on your Sun Solaris server. Be sure to read the database-specific installation guide provided on the DVD/CD and follow the postinstallation configuration instructions. However, ignore any instructions about creating the ArcSDE service; you don't need to do that if you will use direct connections exclusively.

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Installations on the client machine

Making a direct connection to most DBMSs requires that specific files be installed and configured on the client PC. They are as follows:

Oracle
Each client machine on which direct connect is used must have an Oracle client installed and configured.

Microsoft SQL Server
Microsoft Data Access Components (MDAC) must be on the client PCs.

If you intend to use ArcCatalog 9 or ArcView 3.3 with Database Access 2.1f, then MDAC version 2.6 (SP1) or greater is required. If using ArcIMS 9 or ArcGIS 9 to direct connect, you must have MDAC 2.6 or higher.

ESRI recommends you maintain the most up to date MDAC files on your server. Note that MDAC versions beyond 2.8 are included with updates to your operating system.

DB2
Each client machine must be configured for remote database access. Use the DB2 Configuration Assistant on the database host to connect to a remote database.

Informix
Each client machine where direct connect will be used must have the Informix Client SDK 2.8 or the Informix I-Connect 2.8 application installed. The client machine must also have the SetNet32 application installed, which comes with both the Informix Client SDK 2.8 and the Informix I-connect 2.8 applications.

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Client/Database compatibility

In ArcGIS 9.1 and prior releases, when using direct connect, your client and ArcSDE component had to be on the same version, including the same service pack for most releases. For ArcGIS 9.2, your client and ArcSDE component just have to be at the same version—you don't have to have matching service packs.

For example, you can't make a direct connection from ArcMap 9 to a database still in an 8.3 configuration. You would have to run the 9.0 setup configuration on that 8.3 geodatabase to be able to use direct connect from the ArcMap 9 client. If you had installed ArcGIS Desktop Service Pack 3, you would also need to apply ArcSDE 9.0 Service Pack 3 to the geodatabase. However, if you installed ArcSDE 9.2 Service Pack 3, you could still connect to it from ArcGIS Desktop 9.2 Service Pack 2.

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Environment variables

Oracle, DB2, and Informix databases require certain environment variables be set on client machines to connect directly to the database. If you are using one of these databases, consult your DBMS documentation for instructions on which variables to set and how to set them.

ArcSDE applications making direct connections to a DBMS read the parameters from the SERVER_CONFIG table just like the ArcSDE application server. However, not all initialization parameters that apply to the ArcSDE application server apply to ArcSDE applications making a direct connection. For instance, TCPKEEPALIVE and MAXTIMEDIFF do not affect a direct connection.

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Error messages

ArcSDE writes error messages to the following two log files when using direct connect: giomgr_<service>.log file and sdedc_<dbms>.log. If you have the SDEHOME environment variable set, these files will be written here. If you have an etc folder in your ArcGIS installation location, the files will be written here. If you have neither of these, the log files are written to the temp directory.

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Operating system authentication

If you want to connect to your geodatabase from ArcGIS using operating system authentication and your data is stored in an Oracle, DB2, or Informix database, you must use direct connect.

The ArcSDE Personal and Workgroup automatically use operating system authentication and also automatically use direct connect.

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