why does Vary DMCL NC fail to vary a new Disk Journal file online

Document ID : KB000123977
Last Modified Date : 27/12/2018
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Question:
We added a new DISK JOURNAL definition to our DMCL.
Syntax used:
CREATE DISK JOURNAL IDMSDMCL.SYSJRNL4 
FILE SIZE 11000 BLOCKS 
ASSIGN TO SYSJRNL4 

Generated, punched and linked the updated DMCL, allocated and formatted the new Disk Journal file using the new DMCL,  and did DCMT V DMCL NC  and the changes were displayed correctly but the command received  "ERROR Varying File ONLINE".  Why can this new file not be varied online?  
Answer:
In order for the CV to allocate and open a newly defined database or Disk Journal file it would need to know the DSNAME.

  In this case since the startup JCL did not include a DD/DSN for the new Disk Journal file AND the new definition added to the DMCL did not include the DSNAME clause,  the CV cannot know the dataset name to allocate and open the newly created/formatted file.

Example of correct syntax that would allow dynamic allocation for the new Disk Journal file:

CREATE DISK JOURNAL IDMSDMCL.SYSJRNL4 
FILE SIZE 11000 BLOCKS 
ASSIGN TO SYSJRNL4 
DSNAME 'IDMS.CV155.SYSJRNL4'
;