You have those options:
1. you use $ZF(-1) or $ZF(100) to execute a command line from the OS
2. To use embedded python (if your version of IRIS has it) where you can use os. getpid() :
>Write $system.Python.Shell()
Python 3.9.5 (default, Jul  8 2023, 00:24:17) [MSC v.1927 64 bit (AMD64)] on win32
Type quit() or Ctrl-D to exit this shell.
>>> import os
>>> print(os. getpid())
16232

I would try to:
1. check if there is a header for "Content-Length" (the client is setting this)
2. As the %CSP.Request is a stream you might try to check it's "size" property
3. Find the global(s) that are storing this request (not sure which, maybe ^%csp.session or some CacheTemp.csp* with the sessionID - would be a bit complex since its not documented.

The @ (indirection) is not used only to write to a device (spool is a special type of device with number 2).
You may use the @ (indirection) to set any variable, array, list, object property or stream, while keeping this in memory:

To increase your performance there are many factors and test that need to be done in order to take the best action (and approach). Some of them are:

1. Its highly recommended to identify the bottleneck before doing any action.
2. Hardware and infrastructure: Start by monitoring your infrastructure and hardware (network, memory, CPU) to check if there are any bottlenecks. Use task manager (or similar on Linux) to see if one or more disks are exhausted (100% active) - maybe splitting the databases and/or other Cache components (e.g. journals, WIJ, IRISTEMP etc.) between different disks might solve that issue. check if server has enough memory. How many processes are there? is the O/S using swap files when memory is low?
2. Check IRIS (or Cache) related issues: memory usage (are you allocation enough global and routine buffers) heap etc. - are there any errors in console.log that might show any potential issues?
3. Some production related things:
a. Can you run your process in parallel (pool size > 1) - maybe the bottleneck is there
b. Code - is your code optimized - use MONLBL to check the most "overwhelmed" places in your code
c. Journaling & mirroring might slow things if a lot of "temporary data" is journaled and mirrored

This is just the tip of the iceberg... there are many more things that can be done.
If you feel lost, I recommend that you open a WRC to get specific (your system related) help.  

Very nice article. Its exiting to see that Intersystems developers are taking advantage of the (great) Embedded Python feature in IRIS.

If you want to see a "real life" use case (we are using it for more than 2 years in our production environment), check this article: IRIS Embedded Python with Azure Service Bus (ASB) use case | InterSystems
(it also won the 1st place in an Intersystems article competition in 2022)
 

As you probably know, a stream is a "collection" of strings ("under the hood"). As the $ZCRC doesn't support incremental hashing you need to choose some other hashing that support this: SHA-256, MD5 (not recommended due to security vulnerabilities)

We will continue to use SAM for a while. Next year we plan to migrate to "DataDog" monitoring tool which is already being used in our company.
The /api/monitor/metrics/ can be still being used :-) 

I have tested the metrics rest/api and seems that the terminator that is being used is $C(10)

using the /LOGCMD is very useful to log the resulting command line into messages.log so you could have easy access to see from the SMP.

Also, I/O Redirection could be useful for having input, output, errors linked to files (both Linux and Windows)

Could you please give additional information on how the data is being pulled?
You say "tables" so I assume you run a SQL: Is this done by "select" or do you run a SP? 
Is this is a local task on the server (running a COS code) or externally with ODBC/JDBC connection?

I hope that the APIs (e.g. /api/monitor/metrics) will still work, so metrics can still be embeded into any monitoring tool that we are using like dataDog.

Is this correct to assume?

You may use $LISTFIND

$LISTFIND | InterSystems IRIS Data Platform 2023.2
 

Robert, 

WIJ is used to write data to the Db. WIJ holds the copy of Db blocks before they are written to the Db to allow to keep Db integrity (Cache checks if there are "dirty" blocks on WIJ when started, if so writtes them to the Dbs).

"cache buffers" are used to store blocks that were READ from the Db to aviod disk access for concurrent reads

For a-sync mirror membwers, you could use the query:

and then to iterate on result and do the necessary cheeks. 

Great workaround. I remember that I had a problem few years ago that the WebTerminal was unable to do:
ZLOAD routine ZPRINT
I did some (ugly, must say) changes in the broker to let this work
Does your wrapper is able to handle this as well? 

I would recommend that in systems that the audit database is big or huge you stop IRIS and move that database to another disk. Then change in IRIS.CPF (Database section) the location for the audit database. 

Check the user "task2" permissions, maybe this user does not have permission to the audit databse?