Version 7.4.2
 —  Introduction  —

Getting Started

Nuclei start "open" to new users on the local image; on a remote image, they start "closed" to new users on the local image. To modify the status of nuclei throughout the sysplex cluster, see the description of the ADACOM command SN, in section SN - Set Nucleus Status of the Operator Commands documentation.

Note:
ADACOM must be active on the image to use this command.

NUCIDs and DBIDs must have unique values in the range 1 through 65000:

For one operating system image that has cluster nuclei, an additional network target ID is generated that is equal to the cluster database ID. This operating system image "owns" the cluster database and is marked with an asterisk in cluster statistics displays. If all cluster nuclei on that image terminate, Adabas Cluster Services broadcasts the information and another image with active cluster nuclei acquires ownership of the cluster DBID.

Note:
Users and commans coming from systems that are not members of the parallel sysplex (for example, through TCP/IP, a UNIX or PC system) are routed to the image that "owns" the DBID. In fact, this is also true for users coming from members of the sysplex where no ADACOM or cluster nucleus has initialized the sysplex environment.

The document covers the following topics:


First Cluster Nucleus Starts

When a nucleus with a nonzero NUCID starts on an OS/390 or z/OS operating system image, it determines whether the image has a sysplex environment active. If not, it sets up the environment:

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Additional Cluster Nuclei on the Local Image

If another nucleus for the same sysplex cluster comes up on the local image, the global DBID and local image target IDs are already set. The starting nucleus only acquires an IDTE and a nucleus table entry and sets both to its NUCID.

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Additional Cluster Nuclei on a Remote Image

If a nucleus for the same sysplex cluster comes up on another image, it also determines whether the image has a sysplex environment active. If not, it sets up the environment:

This process is the same for all images starting nuclei for the sysplex cluster.

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Images with Cluster Users But No Nuclei

On an image that has users accessing a sysplex cluster but no local nuclei, ADACOM must be executed at least once per IPL to set up the proper environment:

Software AG strongly recommends that you maintain the ADACOM in operation on such an operating system image so that it is available to reset the environment should Entire Net-Work terminate for any reason and restart.

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Environment Maintenance

The following statements apply when Entire Net-Work remains active:

If Entire Net-Work terminates for any reason and restarts, and ADACOM is not active on an operating system image that has users but no cluster nuclei, you must rerun ADACOM on the image to reset the environment. See the section ADACOM for more information.

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Assigning Users to Nuclei

The SVCCLU assigns new users to local image Adabas cluster nuclei, attempting to balance the number of users assigned to each nucleus based on the current number of users.

If no local nucleus is available, the SVCCLU assigns new users to remote Adabas cluster nuclei that are open for users from this image, attempting to balance first the number of users assigned to each image and then the number of users assigned to each nucleus within the image.

A user routed to a remote nucleus is not rerouted when a local nucleus becomes available until the user closes the Adabas session and opens a new one.

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