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Dynamic cross-domain resources z/OS Communications Server: SNA Network Implementation Guide SC27-3672-01 |
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Instead of predefining CDRSCs, you can let VTAM® dynamically allocate and define some or all of them. Dynamic CDRSC definition is used when VTAM receives a request to establish a session from or for an undefined cross-domain resource or for directory search requests. VTAM handles the request by dynamically creating a temporary CDRSC definition for the cross-domain resource. Without dynamic definition of CDRSCs, the number of resources requiring definition can be extremely large. If you provide networking services within an enterprise or for external users, this method is recommended. For example, in Figure 1, if you choose not to predefine a CDRSC for TERM1 and the CDRM definition for HOST11 and HOST31 is set up to allow dynamic CDRSC definition, the following occurs:
When the session-initiation request leaves the first gateway (that is, the gateway NCP connecting NET1 and NET2), VTAM sends out a search to find the real name and NETID to replace the alias name for the destination logical unit if the alias name has not yet been translated into a real name and NETID. For information about how this affects routing, see Name assumption. If no translation takes place in the configuration in Figure 1, the session initiation request means that the destination network is assumed to be NET3 when the request is sent to either HOST31 or HOST32. Following are some advantages of using this method:
Following are the disadvantages of using this method:
Using this method of dynamically allocating CDRSCs is most beneficial for intermediate and destination networks along the session setup path; the destination logical unit real name and network identifier are known by the time the session request reaches these hosts, so replacing CDRSCs is not required. Without dynamic definition of CDRSCs, the number of resources requiring definition can be extremely large. If you provide networking services within an enterprise or for external users, this method is recommended. If the dynamic CDRSC definition is authorized, VTAM does the following actions:
Dynamically defined CDRSC minor nodes are collected in a CDRSC major node named ISTCDRDY. ISTCDRDY is activated automatically during VTAM initialization, and deactivated automatically during VTAM termination. ISTCDRDY can be deactivated and activated by an operator command; this causes all currently active dynamic CDRSCs to be deleted. In addition, all sessions involving dynamically created CDRSCs (including CP-CP sessions with this host, if the partner CP was dynamically defined) are terminated. While allowing dynamic CDRSC definition for session partners in
another domain, you can still restrict access to application programs
using the following exit routines:
Dynamically defined CDRSCs are deactivated and deleted by VTAM on a periodic basis if they are not in use. That is, if a CDRSC has no active sessions and has had none for a defined interval of time, the definition is discarded. This interval is set by the CDRSCTI start option of VTAM. A dynamically defined CDRSC that becomes a shadow resource has all of its sessions moved to the corresponding LU definition. Because of this, it is considered to have no active sessions as soon as it becomes a shadow resource and is then deleted. If dynamically defined CDRSCs are used, initial session initiation time can be slightly longer unless network-qualified names are used in session initiation requests. |
Copyright IBM Corporation 1990, 2014
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