I believe IRIS already can GRANT privileges on schema:

You can use SCHEMA schema-name as the object-list value to grant the object-privilege to all of the tables, views, and stored procedures in the named schema, in the current namespace. The following example grants this user SELECT privilege for all objects in the Sample schema.

GRANT SELECT ON SCHEMA Sample TO Deborah

https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls...

I don't know what happens in your particular case. What you can do -- set logging level in the Web Gateway to "ev2"

"V2" incudus the following information: "Information regarding basic connection management between the Web Gateway and InterSystems IRIS (Start and Close points for each connection)"

Let the Web Gateway run for some time, then hopefully in the csp.log you'll see the details on how new connections are created and old ones are terminated

https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls...

Other idea -- check Apache settings. Which MPM does it use, what recycle settings for worker does it have?

Also, some notes on MPM models of Apache:
https://docs.intersystems.com/iris20232/csp/docbook/Doc.View.cls?KEY=GCG...

This is a standard Windows error with the code 64:

C:\>net helpmsg 64

The specified network name is no longer available.

Some Caché code called some OS system function that returned this error and for some reason it was logged.

To investigate this further -- check what process logged the error message. Find in the Caché Audit a Login event with the corresponding process. Perhaps it might give you some hint

Generally, messages with severity 0 are informational, 1 -- warnings, 2 -- error, 3 -- critical

No. If you have Windows NT authentication enabled to connect to SQL Server then SQL Server ODBC driver uses OS user that executes irisdb.exe process. That's the same use as configured to run service IRIS.

If you'd like to use different user for authentication , then choose SQL Server authentication and specify that user and its password in SQL Gateway connection settings