You cannot delete a record that is already used for any component in the backup infrastructure.
Click Show details to see a list of jobs and components using the credentials record.
Every object in this list must be set to use different credentials before this record can be deleted. Based on the description of the object, follow the instructions below:
Guest OS Credentials
For backup or replication jobs using Application Aware Image Processing, change the credentials in the Guest Processing page of the job settings wizard. In addition to the default credentials specified on this page, the credentials may be specified for specific VMs. Click Credentials, select each object using the account to be removed (if any), and click Set User… to choose a different credentials record. For Oracle VMs, the credentials may be located in the transaction log settings.
For CIFS (SMB), DataDomain, or StoreOnce repositories, select a different credentials record in the repository settings wizard. Note: Exagrid repositories are managed as Linux servers.
Locate the service provider in Backup Infrastructure > Service providers. Edit the service provider properties, and select a different record on the Credentials page.
For Windows, Linux, Hyper-V, vSphere, or vCloud servers, locate the server in Backup Infrastructure > Managed servers. Edit the properties, and select a different record on the Credentials page.
Deny access to the share and modify a File to Tape job, or delete the file share record from the configuration database. See KB2171.
Change the credentials used for storage snapshots in the Storage Infrastructure view.