BIS uses a system resource called a Thread to render pages. For efficiency, BIS maintains an internal pool of threads, and when a request for a BIS page arrives, a thread from the pool is dispatched to serve the page. When the page is completely rendered, the thread returns to the pool to await the next request.
If there are no available threads in the pool, the request must wait for a thread to become available. A request will wait for some period of time (normally about 60 seconds) before being denied with a server too busy error page.
BIS pages that do not communicate with the Service Engine normally execute very quickly. However, if a page contains an XMLExchange tag, the BIS thread serving that page must wait until the Service Engine provides the replacement text for the XMLExchange tag. If this is a lengthy process, it is conceivable that BIS will not have enough threads to serve all pending requests. In this case, it may be desirable to increase the size of the BIS thread pool so more pages can be rendered simultaneously.
The BIS_MAX_THREADS environment variable may be used to increase (or decrease) the size of the thread pool. The syntax is:
|n||Is an integer that specifies the number of threads that will be used by BIS to service requests.|