In addition, Db2 provides a new catalog table, SYSIBM.SYSINDEXCONTROL, to override the  default candidate index processing. Fast index traversal is intended to be automatically  controlled by Db2. Use the SYSIBM.SYSINDEXCONTROL catalog table only to define  exceptions when the automatic processing is unacceptable. Index performance optimization  might be impeded if the number of rows in this catalog table becomes too large. More memory is required to store the fast index traversal memory structures (FTBs). The user  can control the size of this storage area by using the new INDEX_MEMORY_CONTOL  DSNZPARM parameter. The following options are available: Two new IFCID trace records were introduced to track fast index traversal usage. IFCID 389 is  part of statistics trace class 8. It records all indexes that use fast index traversal in the system.  IFCID 477 is part of performance trace class 4 and records the allocation and deallocation  activities of FTBs for fast index traversal. A new DSNI070I console message was also introduced. This message contains information  about fast index traversal memory usage, the number of indexes that use fast index traversal  and the number of candidate indexes. As of this writing, this message is issued only if the fast  index traversal usage changes. DSNI070I features the following format: DSNI070I subsystem-id FAST INDEX TRAVERSAL STATUS: storage-size MB, USED BY:  objects-count OBJECTS, CANDIDATE OBJECTS: candidates-count For example: Db2 12 also introduces a new  -DISPLAY STATS  command to take an instantaneous snapshot  of all the index objects that use the fast index traversal feature. This use of this command  displays the number of index levels and the amount of storage that is used by the index page  set or partition in the fast index traversal storage pool. A typical command uses the format  that is shown in the following example: If the user wants to limit the maximum number of FTBs to be displayed, an integer 1 - 9999  can be specified by using the LIMIT keyword. No option is available to limit the output to a  specific database or index.  When an insert, update or delete operation results in a change to an index non-leaf page in a  Db2 data sharing environment and that index is using fast index traversal, Db2 issues a notify  request to all data sharing members to notify them of the FTB structure change.  Chapter 2. Scalability enhancements and subsystem performance  25 Performance overhead  Fast index traversal memory usage Performance traces and diagnostic messages GLYPH<SM590000> If INDEX_MEMORY_CONTOL= ’AUTO’, Db2 uses a minimum of 10 MB or 20% of the  currently allocated buffer pool storage, whichever is larger. GLYPH<SM590000> If INDEX_MEMORY_CONTOL= ’DISABLE’, Db2 disables the fast index traversal feature  and no FTBs are created. GLYPH<SM590000> If INDEX_MEMORY_CONTOL equals an integer 10 - 200000 (10 MB - 200 GB), Db2  allocates up to the size of the specified value for fast index traversal usage. DSNI070I -DB2A FAST INDEX TRAVERSAL STATUS: 2 MB,  - USED BY: 1 OBJECTS, CANDIDATE OBJECTS: 1 -DIS STATS(IMU) LIMIT(*) 