Prior to IDS Version 9, IDS supported a blocking checkpoint algorithmthat causes the system to block all transactional updates while thebufferpool is flushed to disk. In IDS Version 9 onwards, an additionalcheckpoint algorithm, called Fuzzy Checkpoint, was introduced. FuzzyCheckpoints limit the number of updates required to be flushed to diskduring checkpoint processing.
With the new non-blocking checkpoint algorithm in Cheetah, IDS ensuresthat we virtually don't block transactional updates while the entirebufferpool is flushed to disk. Transactionalupdates are blocked only for very small duration of time required to flush thepartition partitions (tablespace tablespaces) to the bufferpool and tograb the restart point. (Restart point is wherefastrecovery starts. We log the checkpoint and use that LSN as the restartpoint for the checkpoint.)
As part of this feature, the new "onstat-g ckp" command helps DBAs to view and analyze checkpointinformation and performance advisories. The "onstat -g ckp" command isexplained in more detail in thispost.
ScottLashley's whitepaper on developerWorks explains the internalsabout non-blocking checkpoints in detail.
In Part 2, we shall learn how to tune checkpoints and modify the relevant onconfig parameters (RTO_SERVER_RESTART, AUTO_CKPTS,AUTO_LRU_TUNING, etc.)