Resolution:
The nature of the adapter in case of Distributed Queue(RVCMQ) for a single adapter instance is such that there will be only one DQ member working as both the scheduler and the worker.Hence this can perform only one task at a time and is the reason behind the adapter receiving requests sequentially.

For RVCMQ, Multithreading can be achieved by running more than one adapter instance having same distributed queue name and listening on same subject. Worker task and the worker weight needs to be increased as per the requirement.

Note that adapter in RVCMQ will process messages parallelly only if the worker task is more than 1 and multiple instances are started on same CMQ name.