Running Multiple Application Servers at Your Site

Running multiple Application Servers raises the same issues as running multiple SAS sessions. There is little to be concerned with if you set up each server on a different file system. However, quite often, multiple servers could be set up that access the same file system. This raises the general issue of file contention between the Application Servers.

Here are some guidelines to follow if you set up multiple Application Servers on the same file system:

• Servers can share a server root directory.
• Servers can share program libraries. Be sure to use access=readonly when allocating shared program libraries. Allocating shared program libraries in this way prevents an Application Server from opening SAS catalogs in update mode.
• Servers on the same machine must use different port numbers.
• Update access to data sets should be done through the use of SAS/SHARE software. If you do not use SAS/SHARE software and two users attempt to update the same SAS data set at the same time, a failure will result.
• Because update access to files can fail due to operating system contention, Dispatcher programs should be prepared to handle such failures.
• Each server should write to a different log file.