You can tune hardware assisted compression to improve the performance of DUMP processing. With hardware assisted compression, a compression dictionary is built using user data. This dictionary is then used to compress that user data and subsequent user data. Unfortunately, building the compression dictionary is expensive in terms of performance, so it is preferable to avoid building the compression dictionary too often. However, data could be compressed better, resulting in smaller output dump data sets, if the dictionary was rebuilt sooner.

During a physical dump process, the quality of compression is recorded and used in deciding when to rebuild the compression dictionary. Two measurements are used. The first measurement is the quality of compression achieved. This is a percentage, calculated by dividing the compressed size of the data by the original size of the data. A compression is considered poor when the percentage is greater than a threshold value. The default threshold value is 94%.

The second measurement is how many poor compressions are allowed before rebuilding the compression dictionary. The default value for the number of poor compressions allowed before rebuilding the compression dictionary is 15.