RTO_SERVER_RESTART and its effect on checkpoints

The RTO_SERVER_RESTART configuration parameter specifies the amount of time, in seconds, that Informix® has to recover from an unplanned outage.

The performance advantage of enabling this configuration parameter is:
  • Enabling fast recovery to meet the RTO_SERVER_RESTART policy by seeding the buffer pool with the data pages required by log replay.
The performance disadvantages of enabling this configuration parameter are:
  • Increased physical log activity which might slightly impact transaction performance
  • Increased checkpoint frequency, because the physical log space is depleted more quickly (You can increase the size of the physical log to avoid the increase in checkpoint frequency.)
When RTO_SERVER_RESTART is enabled, the database server:
  • Attempts to make sure nonblocking checkpoints do not run out of critical resources during checkpoint processing by triggering more frequent checkpoints if transactions might run out of physical or logical log resources, which would cause transaction blocking.
  • Ignores the CKPTINTVL configuration parameter.
  • Automatically controls checkpoint frequency to meet the RTO policy and to prevent the server from running out of log resources.
  • Automatically adjusts the number of AIO virtual processors and cleaner threads and automatically tunes LRU flushing.

The database server prints warning messages in the message log if the server cannot meet the RTO_SERVER_RESTART policy.

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