Following are the steps to delete unused Software Delivery Packages on the SMP (Symantec Management Platform) Server, Site/Package Servers, and End-point Clients:

1. First of all, so this doesn't happen in the future, make sure that the Default "Delete package from client computer If Unused for:" settings are set in the Default Managed Delivery Settings.  Location: Settings > All Settings > Software > Managed Delivery Settings.  Select the Download Tab and change the "If Unused for:" setting to 1 week, as an example.  This leaves the files on the Client for 1 week after the Policy is no longer active on the client.  You can use a shorter time, like 1 or 2 days, if you would like.  Some packages may have a higher tendency to fail during install, and so you might want a longer Delete date on these packages.  This setting only applies to Clients / Agents, and not Package Servers.
2. End-point Clients Clean-up: In each of the Managed Software Delivery Policy, Package Delivery and Quick Delivery Task ensure to do the following:
   1. Open the desired Managed Software Delivery Policy / Package Delivery / Quick Delivery Task which needs to be deleted, click on ‘Advanced options’ and under ‘Delete a package from client computer’  click on the check-box of ‘If unused for’ and select the anticipated duration when the package needs to be deleted from client.
3. Open the SMP Console and ensure that there are no associated Managed Software Delivery Policies or tasks or jobs for those Software Delivery Packages available.
   1. Locate the Managed Software Delivery Policies under Manage > Policies > Software > Managed Software Delivery {Corresponding Managed Software Delivery Policies}.
   2. Locate the Jobs and Package Quick Delivery Tasks under Manage > Jobs and Tasks > System Jobs and Tasks > Software > Package Delivery.
   3. Locate the Quick Delivery Tasks under Manage > Jobs and Tasks > System Jobs and Tasks > Software > Quick Delivery.
      1. Note - Deleting the Package Delivery / Quick Delivery Task will cause the cleanup process to work.  You can either Delete the Managed Software Delivery policy OR Change the Target (Managed resources) for the clean up process to work with Policies.
4. In the SMP console, delete the required Software Delivery Packages from 'Manage > All Resources > Package > Software Package'. *See Note at the end of this article
5. Site/Package Server Clean-up: Allow for the NS.Package Refresh, NS.Package Distribution Point Update Schedule and NS.Package Server Status Event Capture Item tasks to run on the SMP Server (generally scheduled through the night), for those processes, will clear the Software Delivery Package codebases from the SMP in the SQL database, and the Site/Package Servers will clean up any packages when synchronized with the SMP Server.
   1. Note: The NS.Package Refresh, NS.Package Distribution Point Update Schedule and NS.Package Server Status Event Capture Item tasks can be manually executed from the SMP Server:
      1. Servers: Server Manager > Tools > Task Scheduler > Task Scheduler Library.
   2. Advisory: The synchronization between the SMP Server and Site/Package Servers should clear the unused Software Delivery Packages; however, the Site Server package clean-up schedule may hold packages for that duration.
      1. Configuration on the Console > Settings > All Settings > Notification Server > Site Server Settings > Package Service > Package Service Settings; Delete package files if they are unused for 'SET OPTION' dropdown.

Note:

One thing to keep in mind if you want to delete also the software package(s) on the SMP Server automatically, review the following:

1. Physical packages will not be deleted if their source is the Notification Server (SMP Server), UNC, or URL.
2. Physical packages will be deleted after Software package deletion in SMP Console, only if their source location is "Software Library".
As example:

We have a SW Library specified as UNC location

Imported Software release and specified to import this physical package in our "Software Library" location as source