I'd try to have just 1 query with 3 parameters and switch them on/off as you need

SELECT ID FROM Table WHERE (Field1 %STARTSWITH :par1 
AND ((0=:sw2) OR (
Field2 = :par2)) 
AND ((0=:sw3) OR (
Field3 = :par3))

Now using only par1  means (par1=whatever, sw2=0,sw3=0, par2="",par3="") so the 2nd + 3rd condition is switched off and par2,par3 ignored

2nd case: (par1=whatever,  par2=something, sw2=1,sw3=1, par3="") so only 3rd condition is switched off  par 3 ignored

3rd case: (par1=whatever,  par2=something, par3=other, sw2=1,sw3=1) all conditions active

you see this could be extended easily

before launching your request in your check your %Net.HttpRequest object
property Https is obviously set.

property SSLConfiguration has to be

The name of the activated TLS/SSL configuration to use for https requests.

if the request fails in execution
property SSLError tells you what went wrong

If request uses an SSL connection and a SSL handshake error has occurred, then SSLError contains text describing the SSL error.

more on  %Net.HttpRequest here
http://docs.intersystems.com/latest/csp/documatic/%25CSP.Documatic.cls?P...

It's not yet time for GBLOCKCOPY.
In namespace %SYS you should find a routine ^GCOMPACT
(at least according to docs http://docs.intersystems.com/documentation/cache/cache5docs/PDFS/GMSM.pdf)

Based on the results of %GSIZE you now compact those globals with most blocks and lowest packing.
This generates free blocks that will be eliminated during GBLOCKCOPY.

Routine ^%FREECNT might help you to follow up your efforts
Purpose: Displays the total amount of disk space within a volume group and the amount of free space.

HTH

definitely a good idea to run routine ^%GSIZE  to find the big consumers and packing

directory: c:\intersystems\cache\mgr\user\
Page: 1                           GLOBAL SIZE                        08 Aug 2017
                                                                        10:28 AM
      Global        Blocks       Bytes Used  Packing   Contig.
      --------    --------  ---------------  -------   -------
      CacheStd           1              140      2 %         0
      CacheStdS          1               92      1 %         0
      CacheStream      109          764.376     86 %        70
      ERRORS             1               12      0 %         0
      G1                 1               72      1 %         0

My personal preference is %Status: 1 = OK,
0 = something went wrong + standard or handmade Error Code
+ ability of $system.Status.Append(Status) to get a chain of error messages
which gives you the chance to drill down to the source. Which is especially important when
you get it from some embedded action.

The opposite to me is
<ZSOAP>  that leave you alone with no hint what went wrong
or the famous <ZSG> homed in %Save() Method

to pass return value I prefer objects or variables passed byRef od Output
 
The other opposite is SQLCODE (would be better named SQLerror)  0 is OK. Anything else needs action
But that's tradition in SQL world since more than half a century