This notify message traffic introduces another overhead for GBP-dependent indexes that use  fast index traversal in a Db2 data sharing environment. In our test scenarios, notify message  traffic was observed to be approximately 10 sends and receives every second, compared to  approximately 1.5 sends and receives per second for the tests in which fast index traversal  was disabled, as shown in Figure 2-4. The observed total Db2 CPU time per commit (which includes class 2 CPU time and MSTR,  DBM1, and IRLM address CPU time) shows a 2% reduction when fast index traversal is  enabled (and used), compared to when fast index traversal disabled. The ITR of the data  sharing group improved by 1.3% with fast index traversal enabled.  32  IBM Db2 12 for z/OS Performance Topics Figure 2-4 Notify message traffic: Comparing FTB AUTO and DISABLE 1.35 1.01 9.99 10.06 0 2 4 6 8 10 12 Mem_1 Mem_2 msg. sent/sec. Notify Message Traffic V12R1M500 FTB Disable vs. Auto Disable Auto