Till what time jira maintains the log information?

[Alok Singh]

How much previous details does JIRA maintain inside the log files?

[Paulo Hennig]

Hello Alok, in additional to Shayne response,

The logs created by JIRA are rotated when they reach 20MB. 

This other answer has good guides and an example to delete log files older than 30days using cron.

[Shayne]

The logging is configured to roll over based on file size and can be modified in the JIRA-INSTALL/atlassian-jira/WEB-INF/classes/log4j.properties file:

log4j.appender.filelog=com.atlassian.jira.logging.JiraHomeAppender
log4j.appender.filelog.File=atlassian-jira.log
log4j.appender.filelog.MaxFileSize=20480KB
log4j.appender.filelog.MaxBackupIndex=5

You can find more information on that in the Logging and Profiling documentation.

Our knowledge base article for How to Rotate Catalina Log File may be useful, also.