Contents Lab128 - Tools for Advanced Oracler Tuning and Monitoring. Reference Guide.

Ratio RAC, Cache Fusion Writes

Cache Fusion Writes Ratio - is the percentage of DBWR Fusion writes to the total number of write requests completed by the instance. In other words, it shows the percentage of remote writes to the number of total writes (local + remote). This ratio is defined by formula:

Cache Fusion Writes Ratio = DBWR Fusion writes / (Physical Writes + DBWR Fusion writes)

High ratio is a symptom of frequent updates of same blocks in different instances. It can also indicates inefficient checkpointing or undersized DB cache.