Deferred write processing is a type of processing in which data is written to disk only when the number of updated pages reaches a specified value, instead of data being written each time a COMMIT statement is issued. The point when the number of updated pages reaches the specified value (as determined by HiRDB) is called the deferred write trigger. HiRDB determines the number of updated pages to be written to disk on the basis of the updated output page rate for deferred write trigger that is specified with the -w option of the pdbuffer operand in the system common definition. Deferred write processing cannot be performed for the following RDAREAs:
Overloading caused by input/output processing can be reduced because data is not written to disk each time a COMMIT statement is issued.
Either specify sync or nothing in the pd_dbsync_point operand. In addition, specify the updated output page rate for the deferred write trigger in the -w option of the pdbuffer operand.
If the updated output page rate for deferred write trigger is set to a higher value than is necessary, disk write operations occur more frequently during deferred write processing. This may cause a concurrently executing transaction to be placed in input/output wait status, with adverse effects on the response time.
On the other hand, if the updated output page rate for deferred write trigger is set too low, the number of pages to be written to the database increases, which may cause a concurrently executing transaction to be placed in input/output wait status, with adverse effects on the response time.