ArcSDE Direct Connect Baseline
ESRI recommends use of the Direct Connect as the preferred deployment architecture. Software improvements introduced with the 2004 ArcGIS 9.0 release removed user performance as a potential concern in selecting your ArcSDE configuration. This section provides an overview of why ESRI recommends ArcSDE direct connect as the preferred geodatabase architecture.
ArcSDE Configuration Options
Figure 7a-1 shows the three configuration options for connecting ArcGIS applications to an ArcSDE Geodatabase.
ArcSDE Client Performance Comparison
Figure 7a-2 shows a performance comparison between the ArcSDE Application Server Connect (ASC) and ArcSDE Direct Connect (DC) configuration options. User performance is roughly the same when comparing Unversioned and Versioned database configurations between the two configuration options (versioned geodatabase can perform slower than unversioned). The three tier (remote ArcSDE server) configuration may be slightly slower due to the additional platform communication interface.
Database Server Processing Load Comparison
A closer look at the database server processing load will highlight the real advantages of the direct connect architecture. When using an ArcSDE Direct Connection to the DBMS, the ArcSDE processing load is supported by the client application and not on the DBMS server. The ArcSDE processing load can be as heavy as the DBMS load, so removing ArcSDE processing from the DBMS server doubles the performance capacity of the data server platform. Figure 7a-3 takes a closer look at comparing the data server loads for the ASC and DC configurations. The Direct Connect options reduce the data server processing load by roughly 50 percent.
Database Server Capacity Comparison
There are several potential advantages for having a lighter DBMS server load. Peak capacity processing loads can be supported on a DBMS server with half the number of core (reduce DBMS licensing by up to 50 percent). Larger capacity Enterprise GIS systems can be supported by lower cost server platform technology.
ESRI changed how we license ArcSDE with the ArcGIS 9.2 release - we no longer count the DBMS server core when using an ArcSDE Direct Connect architecture (ArcSDE GSRVR executables not installed on the DBMS server).
There were some limitations with the earlier ArcGIS 9 release that led many users to continue supporting ArcSDE executables on the DBMS server. One limitation restricted client applications from connecting to an earlier release geodatabase (ArcSDE executable will connect only to the same version geodatabase configuration). The ArcGIS 9.3 release includes drivers for connecting direct connect clients to previous version geodatabase schema.
Figure 7a-4 shows the capacity change when using a direct connect architecture. The ArcSDE Direct Connect architecture can increase DBMS server capacity by more than 50 percent.