DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

|This statement contains a Built in Column Function: however, it |
|is not being processed at either Stage 1 Retrieval or Sort Time. |
|In general, this means poor performance, because the column(s) get|
|evaluated only at the end of Stage 2 processing. This might be due|
|to multiple columns used, Group By, not all Stage 1 preds, etc. |
+------------------------------------------------------------------+
ACCESS IS VIA THE CLUSTERING (INSERT & LOAD ORDER) INDEX FOR THIS TABLE
+------------------------------------------------------------------+
|ANL5018W *** ALERT: |
|This clustering (insert) index has a low cluster ratio (below 80) |
|and/or is not well clustered (Clustered flag = N), meaning that |
|inserts are following an unclustered pattern: this is not helpful.|
|You should Reorganize your Table and Index, and re-run Runstats to|
|update these statistics. That should result in better access paths|
|and performance in general. |
+------------------------------------------------------------------+
RANDOM MATCH IX SCAN
--------------------
IX CREATOR: SYSIBM
INDEX NAME: DSNKDX01
VERS: 1 KEY LEN: -1 PADDED: N C-ED: N C-ING: Y CLURATIO: 10.0000
FULLKEY CARD: 25 FIRSTKEY CARD: 25
TYPE: 2 NLEAF PAGES: 34 NLEVELS: 2 UNIQUE: D DUPLICATE OK
2 OF 4 COLUMNS ARE MATCHED CLOSE: N LOCK MODE: IS BPOOL: BP0
KEY COLUMN NAME ORDER TYPE DIST LEN NULL COLCARD DIST#
------------------------------------------------------------------------
1 DLOCATION A VARCHAR N 128 N -1 0
2 DCOLLID A VARCHAR N 128 N -1 0
3 DNAME A VARCHAR N 128 N -1 0
4 DCONTOKEN A CHAR N 8 N -1 0
+------------------------------------------------------------------+
|ANL6052I *** NOTE: |
|This index is specified as "Not Padded", allowing storage of a |
|varying length index key. Padded indexes use blanks to fill out |
|their fixed length keys and are not eligible for Index Only scan. |
|"Not Padded" indexes do not blank fill CHAR and VARCHAR columns, |
|allowing greater flexibility and better use of storage, packing |
|more entries into a single Leaf page. Index Only access allowed. |
+------------------------------------------------------------------+
ALTERNATIVE INDEX
+++++++++++++++++
CREATOR: SYSIBM
IX NAME: DSNKDX02
VERS: 1 KEY LEN: -1 PADDED: N C-ED: N C-ING: N CLURATIO: 0.0000
FULLKEY CARD: -1 FIRSTKEY CARD: -1
TYPE: 2 NLEAF PAGES: -1 NLEVELS: -1 UNIQUE: D KEY COLS: 3
1 A -1 BQUALIFIER
2 A -1 BNAME
3 A -1 BTYPE
+------------------------------------------------------------------+
Appendix C. SQL PA sample reports 403