Today I received a question on the newsgroup about what the different steps of the background processing job are doing as this is not properly documented.
Here is the list of all the steps and what they are doing:
Step 1) Process expired postings
This step does what it says: it deletes expired postings. This step is not enabled per default. This allows authors or editors to update the posting and publish it again with updated content if required.
Step 2) Purge content for deleted pages
MCMS stores placeholder content and custom property values in page objects and publishing properties (start date, expiration date, display name) in posting objects.
Connected Postings use the same page object (that's how the content is shared)
This step will remove the all page objects (including placeholder content, custom property content and resource usage information) and historical revisions of pages that do not have a posting object.
Step 3) Update gallery based resources
This step ensures that attachment and image links to resource gallery items in placeholder content point to the latest revision of a resource gallery item. Historical revisions of the page will still point to the old resource which is still in the database. This step will guarantee that all the placeholder links of the active revision point to the correct content.
Step 4) Purge deleted right groups from container ACLs
MCMS rights groups are assigned to channels, resource galleries and template galleries to implement authorization. When a rights group is deleted then the assignment to the specific container still exists.
This step will remove all the no longer existing rights group assignments from the containers
Step 5) Purge data for deleted resources
Resources, local images and local attachments are stored as so called BLOBs (binary large objects) in the database. When a resource gallery item is deleted or when a page holding a local attachment is deleted then the BLOB of the resource is not removed automatically.
This step will remove all unused BLOBs from the database