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Disabling Caching Clusterwide  



At system startup, the value of a static system parameter controls whether the file system uses a data cache, and if so, which data cache it uses (XFC or VIOC). The system parameter depends on the operating system, as shown in the following table:

Operating System System Parameter Enabled Disabled
OpenVMS Alpha and I64
VCC_FLAGS
1 or 2 (default) 1
0
OpenVMS VAX
VBN_CACHE_S
1 (default)
0

In an OpenVMS Cluster, if file system data caching is disabled on one node, it is disabled throughout the cluster. The other nodes in the cluster cannot use XFC or VIOC until that node leaves the cluster or reboots with VCC_FLAGS or VBN_CACHE_S set to a non-zero value. You can use the DCL command SHOW MEMORY to determine whether caching is enabled.

To disable caching clusterwide, follow these steps on any node in your OpenVMS Cluster:

  1. Set the appropriate system parameter (VCC_FLAGS or VBN_CACHE_S) to 0, using MODPARAMS.DAT.
  2. Run AUTOGEN to ensure that other system parameters allow for the new value. This is not essential, but it is advisable.
  3. You must reboot the system to make the new value effective.

Footnotes
11 selects VIOC; 2 (the default) selects XFC

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