Configuration Parameters
The following parameters affect the behavior of adaptive log file sync:
- _use_adaptive_log_file_sync
- TRUE: Enable adaptive log file sync (default)
- FALSE: Disable adaptive log file sync (i.e., just use post/wait)
- POLLING_ONLY: Use polling with adaptive polling interval
- _adaptive_log_file_sync_use_polling_threshold
- Larger values make it harder to switch to polling
- Default value is 110%, which means the current redo synch time must exceed the expected poll time
- by at least 10% for the algorithm to favor polling over post/wait
- In the pseudocode above, refer to the use_polling_threshold variable
- _adaptive_log_file_sync_use_postwait_threshold
- Smaller values make it harder to switch to post/wait
- Default value is 50%, which means the current scheduling delay needs to drop to half of that when
- polling was first used for the algorithm to favor post/wait over polling
- In the pseudocode above, refer to the use_postwait_threshold variable
- _adaptive_log_file_sync_poll_aggressiveness
- Larger values result in smaller polling intervals
- Default value is 0%, which means none of the current scheduling delay is subtracted from the polling interval
- _adaptive_log_file_sync_sched_delay_window
- The window over which the current scheduling delay is computed
- Default value is 60 seconds, and it is unlikely you need to adjust this
- _adaptive_log_file_sync_high_switch_freq_threshold
- A warning is printed if adaptive log file sync switches frequently between post/wait and polling
- If it is an LRG, a soft assert is also signalled
- Default threshold is 3 switches per minute
- _fg_sync_sleep_usecs
- A non-zero value specified will use polling with a fixed interval and disable adaptive log file sync
- _log_file_sync_timeout
- How long the foreground waits for LGWR to post it when post/wait is used
- Default value is 100 msecs
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