The shared-cache feature was invented many years ago, for use on SymbianOS phones. It was a clever work-around to provide for the concurrency needs of SymbianOS, at that time. But these days, WAL-mode is much preferred, and shared-cache is considered a mistake and a misfeature. Shared-cache continues to be supported because it is a legacy interface that we have promised to maintain backwards compatibility. But we don't like it, and don't want to encourage people to use shared-cache by provisioning it with new capabilities.