PQ84238: Bug in dynacache LRU refresh logic

 Fixes are available

5.1.1.17: WebSphere Application Server V5.1.1 Cumulative Fix 17 for AIX
5.1.1.17: WebSphere Application Server V5.1.1 Cumulative Fix 17 for HP-UX
5.1.1.19: WebSphere Application Server V5.1.1 Cumulative Fix 19 for Linux
5.1.1.16: WebSphere Application Server V5.1.1 Cumulative Fix 16 for AIX
PQ84238; 5.0.2.3: Dynacache LRU update refresh is not working properly
5.1.1.18: WebSphere Application Server V5.1.1 Cumulative Fix 18 for AIX
5.1.1.18: WebSphere Application Server V5.1.1 Cumulative Fix 18 for HP-UX
5.1.1.18: WebSphere Application Server V5.1.1 Cumulative Fix 18 for Solaris
5.1.1.18: WebSphere Application Server V5.1.1 Cumulative Fix 18 for Windows
5.1.1.18: WebSphere Application Server V5.1.1 Cumulative Fix 18 for Linux
5.1.1.17: WebSphere Application Server V5.1.1 Cumulative Fix 17 for Linux
5.1.1.17: WebSphere Application Server V5.1.1 Cumulative Fix 17 for Solaris
5.1.1.17: WebSphere Application Server V5.1.1 Cumulative Fix 17 for Windows
5.0.2.17: WebSphere Application Server 5.0.2 Cumulative Fix 17 for Solaris
5.0.2.17: WebSphere Application Server 5.0.2 Cumulative Fix 17 for Windows
5.0.2.14: WebSphere Application Server 5.0.2 Cumulative Fix 14 for Solaris
5.1.1.10: WebSphere Application Server V5.1.1 Cumulative Fix 10 for Windows
5.1.1.10: WebSphere Application Server V5.1.1 Cumulative Fix 10 for AIX
5.0.2.14: WebSphere Application Server 5.0.2 Cumulative Fix 14 for Linux
5.1.1.19: WebSphere Application Server V5.1.1 Cumulative Fix 19 for AIX
5.1.1.19: WebSphere Application Server V5.1.1 Cumulative Fix 19 for Windows
5.1.1.9: WebSphere Application Server V5.1.1 Cumulative Fix 9 for Solaris
5.0.2.15: WebSphere Application Server 5.0.2 Cumulative Fix 15 for Windows
5.0.2.15: WebSphere Application Server 5.0.2 Cumulative Fix 15 for Solaris
5.0.2.15: WebSphere Application Server 5.0.2 Cumulative Fix 15 for AIX
5.1.1.9: WebSphere Application Server V5.1.1 Cumulative Fix 9 for AIX
5.0.2.15: WebSphere Application Server 5.0.2 Cumulative Fix 15 for Linux
5.0.2.12: WebSphere Application Server 5.0.2 Cumulative Fix 12
5.0.2.14: WebSphere Application Server 5.0.2 Cumulative Fix 14 for HP-UX
5.0.2.14: WebSphere Application Server 5.0.2 Cumulative Fix 14 for AIX
5.1.1.9: WebSphere Application Server V5.1.1 Cumulative Fix 9 for Windows
5.0.2.17: WebSphere Application Server 5.0.2 Cumulative Fix 17 for HP-UX
5.0.2.17: WebSphere Application Server 5.0.2 Cumulative Fix 17 for AIX
5.1.1.11: WebSphere Application Server V5.1.1 Cumulative Fix 11 for AIX
5.0.2.17: WebSphere Application Server 5.0.2 Cumulative Fix 17 for Linux
5.1.1.10: WebSphere Application Server V5.1.1 Cumulative Fix 10 for HP-UX
5.1.1.10: WebSphere Application Server V5.1.1 Cumulative Fix 10 for Linux
5.1.1.9: WebSphere Application Server V5.1.1 Cumulative Fix 9 for HP-UX
5.1.1.9: WebSphere Application Server V5.1.1 Cumulative Fix 9 for Linux
5.0.2.16: WebSphere Application Server 5.0.2 Cumulative Fix 16 for HP-UX
5.1.1.12: WebSphere Application Server V5.1.1 Cumulative Fix 12 for Windows
5.0.2.16: WebSphere Application Server 5.0.2 Cumulative Fix 16 for Solaris
5.0.2.8: WebSphere Application Server V5.0.2 Cumulative Fix 8
5.0.2.16: WebSphere Application Server 5.0.2 Cumulative Fix 16 for Windows
5.0.2.16: WebSphere Application Server 5.0.2 Cumulative Fix 16 for AIX
5.1.1.11: WebSphere Application Server V5.1.1 Cumulative Fix 11 for Windows
5.1.1.16: WebSphere Application Server V5.1.1 Cumulative Fix 16 for Solaris
5.0.2.18: WebSphere Application Server 5.0.2 Cumulative Fix 18 for Solaris
5.1.1.11: WebSphere Application Server V5.1.1 Cumulative Fix 11 for Linux
5.0.2.18: WebSphere Application Server 5.0.2 Cumulative Fix 18 for Windows
5.0.2.18: WebSphere Application Server 5.0.2 Cumulative Fix 18 for HP-UX
5.0.2.18: WebSphere Application Server 5.0.2 Cumulative Fix 18 for AIX
5.1.1.16: WebSphere Application Server V5.1.1 Cumulative Fix 16 for Windows
5.1.1.14: WebSphere Application Server V5.1.1 Cumulative Fix 14 for Solaris
5.0.2.14: WebSphere Application Server 5.0.2 Cumulative Fix 14 for Windows
5.1.1.12: WebSphere Application Server V5.1.1 Cumulative Fix 12 for AIX
5.1.1.12: WebSphere Application Server V5.1.1 Cumulative Fix 12 for Linux
5.1.1.12: WebSphere Application Server V5.1.1 Cumulative Fix 12 for HP-UX
5.1.1.12: WebSphere Application Server V5.1.1 Cumulative Fix 12 for Solaris
5.1.1.11: WebSphere Application Server V5.1.1 Cumulative Fix 11 for Solaris
5.1.1.13: WebSphere Application Server V5.1.1 Cumulative Fix 13 for AIX
5.1.1.13: WebSphere Application Server V5.1.1 Cumulative Fix 13 for Windows
5.0.2.13: WebSphere Application Server 5.0.2 Cumulative Fix 13
5.1.1.13: WebSphere Application Server V5.1.1 Cumulative Fix 13 for HP-UX
5.1.1.15: WebSphere Application Server V5.1.1 Cumulative Fix 15 for Solaris
5.1.1.13: WebSphere Application Server V5.1.1 Cumulative Fix 13 for Solaris
5.1.1.13: WebSphere Application Server V5.1.1 Cumulative Fix 13 for Linux
5.1.1.14: WebSphere Application Server V5.1.1 Cumulative Fix 14 for AIX
5.1.1.14: WebSphere Application Server V5.1.1 Cumulative Fix 14 for Linux
5.1.1.14: WebSphere Application Server V5.1.1 Cumulative Fix 14 for Windows
5.1.1.15: WebSphere Application Server V5.1.1 Cumulative Fix 15 for Windows
5.0.2.18: WebSphere Application Server 5.0.2 Cumulative Fix 18 for Linux
5.1.1.11: WebSphere Application Server V5.1.1 Cumulative Fix 11 for HP-UX
5.1.1.14: WebSphere Application Server V5.1.1 Cumulative Fix 14 for HP-UX
5.0.2.15: WebSphere Application Server 5.0.2 Cumulative Fix 15 for HP-UX
5.0.2.16: WebSphere Application Server 5.0.2 Cumulative Fix 16 for Linux
5.1.1.10: WebSphere Application Server V5.1.1 Cumulative Fix 10 for Solaris
5.1.1.15: WebSphere Application Server V5.1.1 Cumulative Fix 15 for AIX
5.1.1.15: WebSphere Application Server V5.1.1 Cumulative Fix 15 for HP-UX
5.1.1.16: WebSphere Application Server V5.1.1 Cumulative Fix 16 for HP-UX
5.1.1.16: WebSphere Application Server V5.1.1 Cumulative Fix 16 for Linux
5.1.1.15: WebSphere Application Server V5.1.1 Cumulative Fix 15 for Linux
5.1.1.19: WebSphere Application Server V5.1.1 Cumulative Fix 19 for HP-UX



APAR status
Closed as program error.

Error description
cache size is "2" (only 2 entries can be cached)
visit page 1 (we do a "put" to the cache for page 1)
visit page 2 (we do a "put" to the cache for page 2) ... the
cache is now full
visit page 1 (we have a "hit" when we do a "get" from the cache)
visit page 3 ... cache is full, so we need to replace an
existing entry

Our understanding is that the dynacache performs, by default,
a LRU analaysis when the cache is full, in order to "put" new
entries in the cache. In this example, when we visit page 3,
the cache is full. We expect "page 2" to be removed from the
cache, since we most recently visited page 1, and it was found
in the cache (via a "get"). However, page 1 (which was the
first page to enter the cache) is removed to make room for
page 3.
Local fix Problem summary
****************************************************************
* USERS AFFECTED: All dynamic cache users                      *
****************************************************************
* PROBLEM DESCRIPTION: The Least Recently Used (LRU) function  *
*                      of  the dynamic cache is not working    *
*                      properly                                *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
Dynamic cache does LRU analysis to make room for a new entry
when cache is full. Dynamic cache sometimes seems to remove
the most recently used entry instead of the least recently used.
Problem conclusion
This fix makes sure that it is always the least recently used
entry that is evicted when cache is full.
Temporary fix Comments
APAR information
APAR number PQ84238
Reported component name WAS BASE 5.0
Reported component ID 5630A3600
Reported release 00W
Status CLOSED PER
PE NoPE
HIPER NoHIPER
Special Attention NoSpecatt
Submitted date 2004-02-05
Closed date 2004-04-26
Last modified date 2004-04-26

APAR is sysrouted FROM one or more of the following:

APAR is sysrouted TO one or more of the following:

Modules/Macros
dynacach          

Publications Referenced

Fix information

Applicable component levels
R003 PSY    UP
R00A PSY    UP
R00H PSY    UP
R00I PSY    UP
R00P PSY    UP
R00S PSY    UP
R00W PSY    UP


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > General
Operating system(s):
Software version: 00W
Software edition:
Reference #: PQ84238
IBM Group: Software Group
Modified date: Apr 26, 2004