Improve the way HADR retrieve light scan on standby deals with failures such as DISK FULL

When DB2 HADR Standby is behind 2-3TB, it retrieves all files from archives to active log file system and makes the file system full. Standby replays one log file at a time and hence, retrieving thousands of files ahead slows down the replays, makes the active log file system full; Hence, light scan log retrieval will impove the HADR REPLAY on standby databases. IBM case for reference: TS005525495 IBM development team agrees with our finding and proposed solution to provide an option like HADR_SPOOL_LIMIT for this issue; If an APAR can be included in DB2 12.x, it will not only help Department of Homeland Security / Custom and Border Protection but also to many other clients whose database is very large and very active. From IBM HADR development team: Our proposed solutions are: Improve the way HADR standby receive logs so that it prioritizes more efficient method, such as retrieving directly from a shared archive, over others such as log shipping. This should allow HADR Standby to fully utilize the shared archive, until it catches up with primary. Improve the way retrieve light scan on HADR standby deals with failures such as DISK FULL, so that HADR standby stick to log retrieving as much as possible, even if there are temporary errors. Allow user to control the maximum disk space usage in active log path, including both active log files and retrieved log files in subdir of active log path. This prevents HADR standby from using up too many physical disk space when retrieving.