How to best configure persistent queue at tcpout
1. Don't set queueSize in outputs.conf. Leave it to default 0.
2. For IUF/HF/SH/IDX(indexAndForward), set maxQueueSize minimum 20MB to avoid frequent PQ operations.
3. Set persistentQueueSize as per disk space availability.
NOTE: Recently discovered that tcpout can read PQ (assuming PQ has lot of data due to indexing tier outage) at unbounded speed but can not push at the same speed over TCP layer. This results in high memory spike.
Issue is fixed for upcoming 9.4.13/10.0.7/10.2.4/10.4.1 patches.
