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Database Administration
Maintaining and Monitoring Your Database : Managing Performance : Server performance factors : Before-image I/O
Before-image I/O
Before-imaging is always enabled to let the database engine recover transactions if the system fails. This mechanism is extremely important for database reliability, but it creates a significant amount of I/O that can affect performance. In addition, before-image I/O is usually the first and most likely cause of I/O bottlenecks. The engine must always record a change in the BI file before it can record a change in the database and after-image files. If BI activity creates an I/O bottleneck, all other database activities are affected.
You can reduce the I/O impact of before-imaging by:
*Moving the BI file to its own disk
*Running a before-image writer (BIW) on systems with and Enterprise database license
*Providing more BI buffers
*Increasing the BI cluster size
*Increasing the BI block size
*Delaying BI writes
* Monitoring BI activity
* Moving the BI file
* Using a before-image writer
* Providing more BI buffers
* Increasing the BI cluster size
* Increasing the number of BI clusters
* Increasing the BI block size
* Delaying BI writes
* Setting a BI threshold
* Enabling threshold stall
* Using PROQUIET to adjust the BI threshold