4cb7b2e6__s_Manual__Component_Reference__Required
[Attribute] Max Number of Connections [Description] Maximum number of connections allowed in the pool. To ensure that threads don't have to wait for connections, set the max count to the same as the number of threads. In versions of JMeter after 2.3, the value "0" is treated specially. Instead of sharing the pool between all threads in the test plan, a pool containing a single connection is created for each thread. This ensures that the same connection can be re-used for multiple samplers in the same thread. Multiple such pools can be used - e.g. for connecting to different databases - just give them different names. [Required] 
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JMeter - User's Manual: Component Reference
Required