What is the impact of VARY NUCLEUS RELOAD

Document ID : KB000125284
Last Modified Date : 25/01/2019
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Question:
 If I do a NUCLEUS module RELOAD for RHDCOPTF. What is the impact to the running IDMS CV?
 Will things need to be quiesced?
 Can it be done during a busy time on the system?
Answer:
See the SYSTEM OPERATIONs documentation for 

Dynamically Reloading Nucleus Modules

https://docops.ca.com/ca-idms/19/en/administrating/administrating-ca-idms-system-operations/starting-up-a-dc-ucf-system/dynamically-reloading-nucleus-modules 

Regardless of which Nucleus modules are being reloaded, the DCMT V NUCLEUS RELOAD command requires the CV to temporarily come to a Quiesced state while the modules in the Nucleus Reload list are reloaded, then the CV is allowed to resume processing.

The doc indicates the DBA, before issuing the NUCLEUS RELOAD command should be sure the CV Can be brought to a quiesced state 

"When dynamically reloading nucleus modules, be sure to:
  • Bring DC to an inactive state before beginning the reload operation by performing the following steps:
    1. Disable long-running conversational tasks, such as the dynamic system monitor (OPER), the online debugger, and the Realtime Monitor at sites where the CA IDMS/Performance Monitor is installed.
    2. Cancel any long-running jobs that are already active."
 
Quite often on a busy CV the process of bringing the CV to a quiesced state so the Nucleus Modules(s) can be reloaded could take a very long time. 

In most cases, for a busy CV, recycling the CV will be a significantly faster process than the NUCLEUS RELOAD
Additional Information:
https://docops.ca.com/ca-idms/19/en/administrating/administrating-ca-idms-system-operations/starting-up-a-dc-ucf-system/dynamically-reloading-nucleus-modules 

https://docops.ca.com/ca-idms-ref/19/en/ca-idms-system-tasks-and-operator-commands/dcmt-vary-commands/dcmt-vary-nucleus