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## Select activity 

The results from the measurements of the workload that performs SELECT operations against compressed and non-compressed LOBs with different sizes and a varying number of concurrent threads show a similar trend of large throughput benefits for SELECT operations, as shown in Figure 3-3. 

<img src='content_image/1000575.jpg'>

It is worth noting that the overall throughput is comparatively lower for the select case when compared against the measurements that are inserting LOBs. This result is due to (in part) the random nature of the select workload compared to the sequential nature of the insert workload. 

In this scenario, you can see a similar trend where the throughput rate seems to degrade after 20/40 threads for compressed LOBs. 

## CPU performance for insert and select with compressed LOBs 

The zEDC card promises highly efficient compression of LOBs without an affect on CPU performance. This compression is reflective of the CPU performance that was measured in the same environment that was described in 3.1.2, “LOB compression considerations” on page 85. 

Because the zEDC card allows Db2 to rely on the hardware for compression, we did not observe any significant increase in Db2 class 2 CPU time. This result is true for select and insert performance. We noted minor CPU time differences 0.00012 - 0.00014 seconds in the worst-case scenarios (by using 500 KB LOBs with 80 concurrent threads). 

