Undo-only logging Log only the old values of data items. Similar to shadow-paging in that you have to force all the dirty data buffers to disk at commit time. After all the buffers are written, write the commit record. Any transaction that is committed is guaranteed to have all its data on disk, so no redo actions are necessary. Recovery Perform backward pass only.
Recovery is fairly simple.
Must force a lot of data at commit. Redo-only Logging Log only the new values of data items. Assume that during recovery, you never have to undo anything. Make sure that we keep all buffers associated with unresolved transactions in memory. Forbid a dirty page to be evicted from the cache, before its transaction has committed.