[2088510] The account cannot be deleted because it was created using an existing account definition.

It is because the user has an account definition linked to it so it cannot be deleted.They probably have an ADSAccount account definition assigned, check the employee to see.

We just change IsINActive attribute to True on Person table. Then ADSAccount which is assigned to this person changes to disable. (Not physically deleted). An all roles, acc defs are revoked from this Employee by automaticly. We have no current issue now so I can not check the any employee. Because I don't know which employee would get this error when disabled..

What do you mean you say;  'account definition linked to' . All ADSAccounts have an employee, an acc def and manage level in our system. How can I find out these type of accounts? Could you share a simple sql query?

Please take a look at the following regarding how things work with respect to account definitions:

https://support.oneidentity.com/identity-manager/kb/148806/understanding-manage-levels

https://support.oneidentity.com/identity-manager/kb/121947/disabling-employee-account-in-identity-manager-removes-user-account-in-active-directory

You said, "We just change IsINActive attribute to True on Person table. Then ADSAccount which is assigned to this person changes to disable"

This is expected.  See the second KB above as to why.

As to your last question, what type of accounts are you referring to?

The table PersonHasTSBAccountDef will show you all Person accounts with an account definition assigned.

You can query the table ADSAccount for any records with an associated Employee (UID_Person) and the associated account definition (UID_TSBAccountDef) and manage level (UID_TSBBehaviour).

Trevor