It all depends on your learning style.

For me I rather learn as I am building so it was trial by fire as we were migrating from SeeBeyond eGate to InterSystems Ensemble (2014.1) at the time by a certain deadline. I learned a lot on the fly by reading the Developer Community posts, reaching out as needed, and just playing around with the code as I was building it. I also had my company by Cache Objectscript and MUMPS, at least so I can search for a Reference when figuring out syntax. 

The Learning site as a lot of good and informational courses you can take as well.

If I remember correctly, I had to make HSLIB read/write and then I was able to update %SYS when we used ZAUTHENTICATE.mac. We have since moved to using LDAP.

I have used HANG in a code block before to put in a pause between messages when we have two Business Processes sending MFN messages to Epic to update the same Provider record.

I suppose you could write a Custom Ens.Function to do the same within a Rule if you want, or you could route the messages through a Business Process to put the pause in.

If using JDBC you can use a JDBC SQL Software like DBeaver or Squirrel SQL.

DBeaver officially supports InterSystems IRIS | InterSystems Developer
How to create a database connection in DBeaver - DBeaver
 

With some help we created a function to loop through a repeating field and verify values against a single string, and a variation against a Lookup Table...

ClassMethod DoesSingleValueExistRepeatingSegmentFields(pHL7Msg As EnsLib.HL7.Message, pSegment As %String, pField As %String, pSubField As %String, pInputValue As %String) As %Boolean

{

   #dim tSeg as EnsLib.HL7.Segment

   set tSegCount = pHL7Msg.SegCountGet()

   set i = 1

   set j = 1

   Set tFound = 0

   //get new values

   set tval=""

   while ((i <= tSegCount) && (tval="")) {

     set tSeg = pHL7Msg.GetSegmentAt(i)

     if (tSeg.Name = pSegment) {

      set pField2 = pField_"(*)"

      set tRepCount = tSeg.GetValueAt(pField2)

      while ((j <= tRepCount) && (tval="")) {

        set tID = tSeg.GetValueAt(pField_"("_j_")"_"."_pSubField)

        if (pInputValue = tID) {

         set tval = 1

        }

       set j = j + 1

      }

     }

     set i = i + 1

   }

   if (tval '= "")

   {

      Q 1

   }

   quit 0

}

If you are running Windows maybe it’s the Windows Defender Firewall on your local machine?

Do you have to use Result Set, why not use EnsLib.SQL.Snapshot as a context variable, and using a While loop call the Snapshot.Next() to loop through the results to do what you need to do?

For example.... I make calls to a Stored Procedure then use the Snapshot that is returned to fill in other properties that I need...

<call name='Ref_PrivilegeForm' target='CREDVerityMFNCPDWriteDev' async='0' xpos='200' ypos='350' >

<annotation><![CDATA[Execute stored procedure to insert/update the PrivilegeForm value sent by Verity into the Ref_PrivilegeForm table, and return the identity key]]></annotation>

<request type='osuwmc.Credentialing.DataStructures.RefPrivilegeForm' >

<assign property="callrequest" value="context.RefPrivilegeForm" action="set" />

</request>

<response type='EnsLib.SQL.Snapshot' >

<assign property="context.Snapshot" value="callresponse" action="set" />

</response>

</call>

<while name='Snapshot.Next()' condition='context.Snapshot.Next()' xpos='200' ypos='450' xend='200' yend='350' >

<assign name="PrivilegeFormKey" property="context.PrivilegeFormKey" value="context.Snapshot.Get(&quot;PrivilegeFormKey&quot;)" action="set" xpos='200' ypos='250' >

<annotation><![CDATA[aka Index]]></annotation>

</assign>

</while>

<assign name="reset Snapshot" property="context.Snapshot" value="&quot;&quot;" action="set" xpos='200' ypos='550' />

We have a shell script that we executes that signs in via Terminal and calls EnableConfigItem to start or stop an Object within IRIS. We found that running this at the OS level allows us to be more multithreaded than the Scheduler within IRIS.