Hello @Adarsh.op 

Thanks for the great question. First off we need to check the following: 
https://kb.commvault.com/article/53950

Symptoms

A Data Protection or Auxiliary Copy job fails to use Appendable Media when it appears that Appendable Media is available.

Causes

Appendable media usage conditions have not been met. Appendable media is NOT selected for reuse only under the following conditions:

• When the media belongs to a different storage policy.
• If there was only one qualified appendable media and it was the last written media in that storage policy. In such a case, at least one spare media must be available before the system will use the appendable media. This is to ensure that the condition that caused the media not to be filled (marked appendable) is cleared.
• Synthetic full backups will  not use Appendable media.
• A job option which has the Start New Mediaoption enabled, will not use appendable media.

Resolution

Verify that Appendable Media Usage Rules listed above have been met. Also check the Use Appendable Media within n Day (s) of its last write time option in the Library Properties (Media) tab to see if it is enabled, the number of days established for the option, and whether it meets the usage requirement.

If we have checked the above and we still don’t have our answer then we might need to look at your multiplexing level and if “Stream Randomization is turned on for your storage Policy at the top level: 

 

Kind regards
Albert Williams

Hi Williams,

Thanks for your valuable reply, I will check and update you