With the system task named "Cleanup Submitted Tasks" I'm not able to reset (to empty completely) the TP database.
Is there any SQL statement or procedure to accomplish that result?
There is a procedure that archive the data from task persistence to the archive database. I used these procedures on version 12.6.2:
Stuck In Progress Tasks / Events & Garbage Collection
I don't know if in version 14.2 will work, but you can try this in a non-production environment, or, you can open a support case, they sent it to me when I needed it.
It is important to know that there are some RDBMS structural changes from 12.6 to 14.2 for Task Persistence. Please review the scripts against the SQL/DDL to ensure that all the items are covered.
If purpose is to completely empty the Task Persistence db tables then I guess the easiest way is to recreate them through the script (Microsoft SQL Server: C:\Program Files\CA\Identity Manager\IAM Suite\Identity\tools\db\taskpersistence\sqlserver\idm_db_sqlserver.sql) used to install them in separate database.
refers to IM Guide
Run the SQL Scripts - CA Identity Manager - 14.2 - CA Technologies Documentation