DB2 - Problembeschreibung
Problem IC72243 | Status: Geschlossen |
Optimizer may choose a non-optimal plan for queries using FETCH FIRST ROWS ONLY caluse, which can cause performance degradation. | |
Produkt: | |
DB2 FOR LUW / DB2FORLUW / 970 - DB2 | |
Problembeschreibung: | |
Optimizer may choose a non-optimal plan for queries using FETCH FIRST ROWS ONLY (FFNR) caluse, which can lead to performance degradation. This plan causes a large stream of data to be broadcasted across partitions. Users will find this evident in the query access plan, which will show the BTQ operation broadcasting large stream of data as following: /-------- 1.07181e+07 BTQ ( 13) 125531 31015.2 | 2.67952e+06 IXSCAN ( 14) 123504 31015.2 | 2.67952e+06 INDEX: <name of the index> In this example, aprox 1.07x10^7 rows are being broadcasted across partitions. This leads to poor performance. | |
Problem-Zusammenfassung: | |
USERS AFFECTED: =============== Customer using version 9.5 and above on all platforms. PROBLEM DESCRIPTION: ==================== Queries using FIRST FIRST ROWS ONLY (FFNR) clause may experience performance problem after migrating from version 8 to version 9. The APAR can be confirmed by checking the query access graph. If a BTQ operation is seen broadcasting large stream of data, it may point to this APAR. RECOMMENDATION: =============== There is currently no workaround other than not using the FFNR clause. | |
Local-Fix: | |
verfügbare FixPacks: | |
DB2 Version 9.7 Fix Pack 4 for Linux, UNIX, and Windows | |
Lösung | |
Problem is first fixed in version 9.7 Fixpack 4. | |
Workaround | |
There is currently no workaround other than not using the FFNR clause. | |
Weitere Daten | |
Datum - Problem gemeldet : Datum - Problem geschlossen : Datum - der letzten Änderung: | 27.10.2010 03.05.2011 03.05.2011 |
Problem behoben ab folgender Versionen (IBM BugInfos) | |
9.7.FP4 | |
Problem behoben lt. FixList in der Version | |
9.7.0.4 |