Not clear if you are using a script to rotate the logs or standard web agent parameters (either Local or ACO)?
I have found that using web agent paraments works best . . .
Within either the Agent Configuration Object (Policy Server) or LocalAgent.conf (Web Server)
LogFileSize=xx < sets the maximum Log File Size before rolling (i.e. 50 = 50 MB)
LogFilesToKeep=xx < maximum number of log files to keep before truncating (i.e. 10 = 10 + 1~current)
TraceFileSize=xx < sets the maximum Trace Log File Size before rolling (50 = 50 MB)
TraceFilesToKee=xx < maximum number of log files to keep before truncating (10 = 10 + 1~current)
NOTE: Above will consume a max of 549 MB disk usage.
It may be worth noting that Agent Log files are normally not that large, so 10 MB file size may be adequate. However, Trace files contain useful troubleshooting data - but keeping the at 50 MB makes diagnosing their content easier. You may need to set the number of trace files to keep at 20-30 (1G-1.5G disk usage), I find 25 trace files at 50 MB can cover 5-7 days worth of data. You may need to examine to determine what works best in your case. Also, you can always use a script to copy the oldest (2-4) logs (name-date-time.log) to an archive folder.
More details can be found here <List of Agent Configuration Parameters - CA Single Sign-On - 12.52 SP1 - CA Technologies Documentation>
NOTE: You may want to consider upgrading the a new version of SiteMinder < not meant to be a sales pitch.
Take care,
Kirk (Leslie Kuykendall)