Automatic checkpoints, LRU tuning, and AIO virtual processor tuning

The database server automatically adjusts checkpoint frequency to avoid transaction blocking. The server monitors physical and logical log consumption along with information about past checkpoint performance. Then, if necessary, the server triggers checkpoints more frequently to avoid transaction blocking.

You can turn off automatic checkpoint tuning by setting onmode -wf AUTO_CKPTS to 0, or setting the AUTO_CKPTS configuration parameter to 0.

Because the database server does not block transactions during checkpoint processing, LRU flushing is relaxed. If the server is not able to complete checkpoint processing before the physical log is full (which causes transaction blocking), and if you cannot increase the size of the physical log, you can configure the server for more aggressive LRU flushing. The increase in LRU flushing impacts transaction performance, but reduces transaction blocking. If you do not configure the server for more aggressive flushing, the server automatically adjusts LRU flushing to be more aggressive only when the server is unable to find a low priority buffer for page replacement.

If the VPCLASS configuration parameter setting for AIO virtual processors is set to autotune=1, the database server automatically increases the number of AIO virtual processors and page-cleaner threads when the server detects that AIO virtual processors are not keeping up with the I/O workload.

Automatic LRU tuning affects all buffer pools and adjusts lru_min_dirty and lru_max_dirty values in the BUFFERPOOL configuration parameter.

Copyright© 2019 HCL Technologies Limited