cached memory is 100% for LTM

It looks like a metric of ramcache utilization. 100% Usage in this case is perfectly normal. TMOS does not allow more than x % of RAM to be utilized for caching (webacceleration). Webacceleration (previously known as ramcache) will cache objects until the memory allocation limit is reached, or until there are no objects left to cache - whichever comes first.

You may expect to see lower utilization percentage during low-activity hours. During normal or high activity hours, this metric should always stay near 100%, therefore, I see no good reason to monitor ramcache utilization.

You can see the current limit by typing in the command below:

tmsh list sys db ramcache.maxmemorypercent