Some nodes say that I/O Express is not installed on all nodes

Check the number of Cluster Descriptor Table Entries (CDTEs) available to the system. If there are not enough CDTEs available to establish communication between nodes, the driver will be loaded but a given node will not be able to communicate with other nodes in the cluster. The number of CDTEs is controlled by the SYSGEN value SCSCONNCNT. The default value for CDTEs is 40. However, in a cluster of more than four nodes, this value will not be high enough to allow I/O Express to establish communication across all nodes.

With the introduction of VMS v5.5, a cluster without I/O Express should have seven CDTEs per node. I/O Express needs an additional CDTE to establish its communication. Therefore, to determine how many CDTEs you should have for your system while running I/O Express, multiply the number of nodes in the cluster by 8. Then, add 12 to that figure in order to allow two more nodes to join the cluster without raising the SYSGEN parameter SCSCONNCNT each time a node joins the cluster.

For example:

9 (nodes in the cluster)

8 (number of CDTEs needed per node with I/O Express)

----

72

+12 (Safety factor to allow two more nodes to join the cluster)

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84 (Total number of CDTEs as a minimum for a nine node cluster)

To determine if the problem is caused by insufficient CDTEs, log into one of the nodes that according to IOX SHOW CACHE does not have I/O Express loaded. At the dollar prompt type:

              
                
                  $ SET PROCESS/PRIV=CMKRNL$ ANALYZE/SYSTEM 
                
              
            

Next, at the SDA> prompt, type:

              
                
                  SDA> SHOW CONNECTIONS 
                
              
            

This will list all the CDTE addresses on the system. If a CDTE address is associated with a Local Process in the "Listen" state, the CDTE is available. If the CDTE address is "Open" it is connected to a node in the cluster. There should be one CDTE address associated with an I/O Express process for each node in the cluster. At the end of the CDTE summary, a message will display the number of free CDTEs. If there are less than twelve free CDTEs and not all the nodes in the cluster have an I/O Express process associated with a CDTE address, you should increase the number of CDTEs.

Executive Software Europe