This is a brilliant strategy, because Oracle can quickly make the minimal amount of changes necessary to record a change in a block, yet still maintain concurrency control at the row level. The final bock changes will eventually need to be made, but perhaps that will occur at less intense workload period, such as after a benchmark has completed.

To see a wonderful example of this, Figure 6-39 shows the inactive transactions flag change as a direct result of issuing a simple a select statement that touches block 1,78547.

Figure 6-39. Shown is a data block (1,75847) dumped immediately after a simple select statement touched the block. Notice the transaction flags have changed from a --U- to a C---, indicating a block cleanout has occurred.