The baseline test was run by using Db2 11 NFM. Then, the second test was done after  migrating to Db2 12 at function level V12R1M100, and after REBINDing all application  packages that use APREUSE(ERROR) to preserve the access paths from the Db2 11 NFM  baseline test.  The third test was done after activating Db2 function level V12R1M500, and a REBIND of all  packages with APREUSE(ERROR), which allowed the workload to run at a higher function  level and keep the access path of the Db2 11 NFM baseline test.  The fourth and final test was done with Db2 at function level V12R1M500 and a REBIND of all  packages, this time with APREUSE(NONE), which allows new access paths to be selected  for applications when applicable. As before, all scenarios use plans and packages that are  bound with RELEASE(COMMIT). The measurements were performed by using the following environment:  Many internal optimizations and enhancements apply to Db2 12 that are not applicable to  older Db2 releases, which contributes to the performance improvement of Db2 12 at function  level V12R1M100 (and above). The following internal optimizations and new features are  included:  At function level V12R1M500, Db2 12’s fast index traversal feature can also be used for index  objects that are group buffer pool dependent when they meet the fast index traversal criteria.  This feature can increase the performance benefits the fast index traversal functionality  provides. REBIND with APREUSE(NONE) allows new access paths to be selected (when  applicable), which introduces the possibility that better access paths are picked to achieve  better application performance. Figure 5-5 on page 169 shows the getpage reduction per transaction for the different  migration scenarios. The getpage reduction (when going from Db2 11 NFM to Db2 12 at  function level V12R1M100) is the result of the fast index traversal feature, although the usage  is limited to non-GBP dependent index objects.  The reduction in the number of getpages when going from function level V12R1M100 to  V12R1M500 is because at that function level, GBP-dependent indexes can also use the fast  index traversal feature. 168  IBM Db2 12 for z/OS Performance Topics GLYPH<SM590000> The use of a new PL/X compiler for Db2 12 performance sensitive modules. GLYPH<SM590000> Log latch relief (LC19). GLYPH<SM590000> The use of the fast index traversal feature is available at function level V12R1M100, but  only for non-group buffer pool-dependent index objects. GLYPH<SM590000> Two z13 LPARs with six general CPs each. GLYPH<SM590000> Two internal coupling facilities (ICF) with three dedicated CPs each. GLYPH<SM590000> Four ICPs and four CIBs are shared between two LPARs and two ICFs. GLYPH<SM590000> z/OS 2.2 and CFCC Level 21.