How can ITKSTC reuse system LXs?

Document ID : KB000115346
Last Modified Date : 11/10/2018
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The Health Checker for one of our LPARs gave the info, that we only have a few number of available system LXs. When we run the check in the VERBOSE option, we get a report which shows, that the ITKSTC on this LPAR blocks several system LXs, status dormant. When an address space that owns a non-reusable system LX terminates, the LX becomes dormant. We restart the STC once a day. How can define that the STC reuses the LX?  
Our ITK started task always obtains a new linkage index during a cold start and always reconnects to an existing one during a warm start. We confirmed this on our system on release 20. So, the solution is to use a warm start unless cold one is absolutely necessary. 
Additional Information:
We changed the start options yesterday and at the moment, we start the STCs once a week.
In the past we had a problem because of only restarting the STCs during IPL, but at the moment we can't remember which problem it was. This was the reason for restarting it every day.