PoolSize is an Integer property that indicates the number of thread instances to allocate to the internal thread pool for a thread-based scheduler. The default value for PoolSize is 0, as assigned during initialization of the component, and indicates that no thread instances are allocated to the internal thread pool. 

PoolSize is used in the Init method which allocates thread instances to the internal thread pool at runtime. 

PoolSize is also used in the ReleaseYarn method to determine if the thread reference for the freed yarn should be returned to the internal thread pool. 

PoolSize is used only when loading the component (component streaming) or when new threads are required in AcquireYarn. 

Setting PoolSize to a large value will lead to longer load times. 

Setting the value in PoolSize after a server has become active will result in thread instances being accumulated after execution in the thread pool until the number in PoolSize is reached.

TIdThreadSafeList 

Init 

ReleaseYarn 

AcquireYarn