A technique for operating a high-availability (HA) data processing system includes, in response to receiving an HA logout indication at a cache, initiating a walk of the cache to locate cache lines in the cache that include HA data. In response to determining that a cache line includes HA data, an address of the cache line is logged in a first portion of a buffer in the cache. In response to the first portion of the buffer reaching a determined fill level, contents of the first portion of the buffer are logged to another memory. In response to all cache lines in the cache being walked, the cache walk is terminated.