Cache structure reclaim avoidance

A system-initiated alter for an eligible cache structure with data elements may also begin in an attempt to avoid reclaims for directory entries. Structure full monitoring assumes directory entry reclaims are imminent when the total in use (changed and unchanged) percentage of directory entries exceeds 95% of the total directory entries. When this threshold has been exceeded and the size of the structure is larger than 20 megabytes, a system-initiated alter may begin. In this case, the structure size is not expanded, but the structure objects may be reapportioned to provide more cache directory entries at the expense of data elements. System-initiated alter processing will only attempt to increase the entry/element ratio to a maximum value of 255:MAXELEMNUM. MAXELEMNUM refers to the IXLCONN MAXELEMNUM attribute of the structure specified by the application instance that allocated the cache structure.