Information on PSAPPSRV, PSQCKSRV, and PSQRYSRV, PSQCKSRV processes and their impact on PS Queries

Are PSAPPSRV, PSQCKSRV, and PSQRYSRV processes different?
No. The PSAPPSRV, PSQCKSRV, and PSQRYSRV processes are basically the same program. 


Since PSAPPSRV, PSQCKSRV, and PSQRYSRV processes are the same, why you need three versions of the same process?
They are named differently to facilitate handling specific types of jobs to divide the load of the domain.


However, there are quite a few differences on their usage and impact on the performance of PS Queries. I am sharing my little knowledge on these processes.
PSQRYSRV and PSAPPSRV processes:
If the PSQRYSRV process is not started, PSAPPSRV process will take over PSQRYSRV’s job and complete it. The hiccup is that it could have an impact on the performance and slow it down.


PSQRYSRV process:
PSQRYSRV process should be started right during the domain configuration. Minimum 1+ PSQRYSRV process should be started. This is to support running of multiple queries by multiple users on the web.


Then what is PSQCKSRV process?
The PSQCKSRV process supports queries running in 2-tier and/or 3-tier. This process is not used on the web and should be started only when using it in 2-tier and/or 3-tier.


Links to my other posts on PS-Queries and Query Administration:

1. Why a Service or PS-Query request runs twice though it is submitted only once from PIA?
2. All about PeopleSoft Query Administration
3. All my previous posts on PS Queries