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You have to remember that access restrictions are inherited from its parent collection only when items are submitted, not when access restrictions are modified. So the any new items submitted to that collection will have the collection's restrictions you set, but existing items will keep their current permissions.

In other words: "When a new item gets archived in the repository, it inherits the default policies for an item, defined by the collection in which the item is archived. It's important to realize that these policies can altered for each item, bundle or bitstream, without altering other items or collection properties. Policies are really tied to items, bundles and bitstreams." (source)

So how would you do a mass-change of permissions?

• In XMLUI, use Advanced Policy Manager. Log in as an administrator, in the Administrative menu, click Authorizations (under Access Control.) Then in the main pane, under the search box, there's a link to the tool (Advanced authorizations tool: Click here to go to the item wildcard policy admin tool).  See also this video guide: https://youtu.be/PFlq-yGSPY4
• You can write a curation task (DSpace 1.7 and newer, see DSpace 1.8: Curation System, Curation Task Cookbook)
• You can write custom SQL query on the "resourcepolicy" table. On newer DSpace versions which use Discovery,
  • In order to see this changes take effect in the UI (in Discovery search/browse), be sure to update the discovery index (using the -f flag) after running the SQL query.

How do I remove the search box from the front page in XMLUI?

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