Pathway/iTS System Management Manual (G06.24+)

Tuning Your System Using Statistics
HP NonStop Pathway/iTS System Management Manual—426748-002
5-2
Link Management
Link Management
Links enable communication between requester programs and server programs. The
TCP coordinates the sharing and dissolving of links between SCREEN COBOL
requester programs and server programs.
The following list describes the properties of links:
•
A link results in a single open of a server with a nowait depth of 1. This open is
available for use by multiple requesters on a serial basis.
•
A link can be used for one send operation at a time.
•
A link between the TCP and a server process is busy when it is being used by a
terminal task to communicate with a server; otherwise, it is available.
•
Links become available when:
•
A busy link is freed by its user.
•
A new link to the server class is requested from and granted by the PATHMON
process.
•
For link management, two queues are maintained: LINK and DELINK.
Establishing Links
A terminal task requests an available link by executing a SCREEN COBOL SEND
statement. (The link becomes available at the end of the SEND statement.)
When the TCP interprets the SEND command, it checks to see if an existing link is
available:
•
If an existing link is available, the TCP allocates the link to the requesting task and
SEND processing continues.
•
If an existing link is not available, the terminal task of the TCP can do one of these:
•
Join the link queue associated with that server class.
•
While on this queue, the terminal task is blocked from execution. When an
available link is assigned to the task, the task is activated.
•
Request a new link from the PATHMON process.