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I am implementing AbstractRoutingDataSource in our project. From what i read
AbstractRoutingDataSource is an abstract data source implementation
that routes getConnection() calls to one of various target DataSources
based on a lookup key. The latter is usually (but not necessarily)
determined through some thread-bound transaction context.
What I am wondering is ,what is the advantage of using a thread bound transaction context to determine the lookup key? When is it ideal to use such a method. Any help would be highly appreciated. Thanks in advance :)

Briefly, Bound Threads can change the attributes of the underlying lightweight process. and Lightweight processes are not cached when the bound threads exit.
In Scheduling Context; Bound threads for System Scope and Unbound threads are Process Scope. [Docs Oracle, 2010]
System Scope: compete for CPU with other system threads (such as Kernel Threads).
Process Scope: compete for the CPU within the current process.