It is recommended that the CM should be shutdown when deleting the files. This is to avoid any reference being made by a running concurrent program to the file in cache directory. Refer the below note. This is applicable for R12.2 as well.
How To Delete The XML, TXT Files From /U02/Inst/Apps/Prod_prod/Logs/Ora/10.1.2/Reports/Cache (Doc ID 1200864.1)