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OpenVMS Cluster Credit Waits?

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The Question is:

We have a cluster of 4 AlphaServers (8400s) set up in two sites running VMS
 6.2-1H3 and quite often see credit waits across the fddi intersite links.
I noticed that vms7.1 has a new sysgen param (cluster_credits) which allows
 increasing the number of credits from the default of 10.
It'll probably be a while before we move to 7.x and I was wondering if this
 feature has been implemented as a patch kit for version 6.x
Failing that is there any (safe) way of modifying this ourselves. A brief look
 seems to indicate that the number of credits is set in clu$gl_cluster_credits
 but I realise that other code may make assumptions based on the default value
 and also assume that
 any code to change this would need to run _very_ early in the startup (perhaps
 so early that it would be impossible to do). This option is more out of
 curiosity than any serious intent to do something about it so if the answer
 involves any serious resear
ch then skip it.

The Answer is :

  As for the question, in V7.1 and later, the CLUSTER_CREDITS system
  parameter is used on the CONNECT and ACCEPT calls that create SCS
  connections, and is used to size various data structures and paramters
  used by the cluster connection manager.  In order to effect similar
  changes in prior versions, you would have to write code that executes
  very early in the boot process (during EXEC_INIT just after).  Frankly,
  it would be easier to upgrade to V7.2.
  Are you certain that the credit waits are caused by the connection
  manager (VMS$VAXcluster)?  If they are caused by the MSCP server, you
  can improve the situation by using the MSCP_CREDITS system parameter,
  which does exist in V6.2.
  If you applied sufficient "patches" to V6.x to implement all the new
  features in V7.x, at what point would system be declared to be running
  In other words, yes, the "patch kit" exists. It's rather large, and
  it more commonly goes by the name "V7.1 upgrade"
  Alternatively, you could upgrade to V7.1, V7.1-2, V7.2, V7.2-1, etc,
  and set the system version string back to, say, V6.2.

answer written or last revised on ( 21-APR-2000 )

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