WAS의 JSession ID 중에 cache ID 가 지속적으로 증가

1. WAS 버전 : WAS ND v6.1 이하 버전

2. OS : All

3. Error 발생 시점 :  Session persistence 를 사용하고 동일한 브라우저에 연속해서 여러 웹 어플리케이션에 접속했는데
                            지속적으로 JSession ID 중에 cache ID 가 증가

4. Error message :                         
           JSession ID 가 "0000HHAnbYWnNxGD-iVupvcArfr:14dtuueci" 라면 맨 앞 4자리 "0000" 이 cache ID

5. 예상 이유 : WebSphere 의 구조상의 이슈

6. 조치 방안 :
 지속적으로 cache ID 가 증가되어도, 실제적으로는 Session ID 만 활용되므로 운영에는 문제가 없지만 이를 방지하기 원한다면
 Fixpack 6.1.0.13 이상이 적용되어 있어야하며, Web container 의 사용자 속성에 OptimizeCacheIdIncrements 를 true 로 지정

OptimizeCacheIdIncrements
    Set the OptimizeCacheIdIncrements custom property to true to make the session manager assess whether the in-memory session is older than the copy in persistent store. Setting this property resolves the continually increasing cache ID.

    If HTTP session management is configured to use session persistence and the user's browser session is moving back and forth across multiple Web applications you might see extra persistent store activity as the in-memory sessions are refreshed from the persistent store. As a result, the cache IDs are continually increasing and the in-memory session attributes are overwritten by those of the persistent copy. To prevent the cache IDs from continually increasing, use the following name-value pair:

    If the configuration is a cluster, ensure that the system times of each cluster member is identical as possible.
    Avoid trouble: You must have Fix Pack 6.1.0.13 or higher installed on your system before you can use this custom property.


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