Disclaimer: I do not have any 1st-hand experience with DB2.
Herewith the NBU8 for DB2 manual: https://www.veritas.com/content/support/en_US/doc/ka6j00000000AAyAAM
I have read through the section under About log archiving. I do not see anything that says User Exit method is required?
Not sure if it will help, but herewith a post where a user managed to solve his own problem:
https://vox.veritas.com/t5/NetBackup/Redirected-DB2-restores-error-out-with-SQL2062N-an-error/td-p/371156
The Symantec links in the post should redirect to these Veritas links:
https://www.veritas.com/support/en_US/article.TECH51846
https://www.veritas.com/support/en_US/article.TECH77284
Hope this helps.