OK, no punctuation, no empty words, etc.... My lowest bid: 74 chars

ClassMethod Order(s)
{
	f  s p=$p(s," ",$i(i)),w=$tr(p,1/17),$p(z," ",$tr(p,w))=w ret:p=w $g(z)
}

By the way, the following three variants all have the same size of 74

	f  s p=$p(s," ",$i(i)),w=$tr(p,1/17),$p(z," ",$tr(p,w))=w ret:p=w $g(z)
	f{s p=$p(s," ",$i(i)),w=$tr(p,1/17),$p(z," ",$tr(p,w))=w ret:p=w $g(z)}
1	s p=$p(s," ",$i(i)),w=$tr(p,1/17),$p(z," ",$tr(p,w))=w q:p=w $g(z) g 1	

You say "No punctuation". OK, but then we have a contradiction: Example 4 of the test cases contains several commas, a dot and a question mark...

A small complaint:
- possible word delimiters weren't specified (space, tab, etc.)
- no specification about punctuation marks (allowed or disallowed)
- no specification about empty words (allowed or disallowed) and how to handle them, if allowed

So my question is, are the following examples legal or not:

"O2K. I'1m" --> "I'm OK."
"spac4es are2    1There     ma3ny" --> "There are many spaces."

Putting all in one line saves one byte

ClassMethod Order(s As %String) As %String
{
	s d=" ",z="" f i=1:1:$l(s,d){s b=$p(s,d,i),c=$zstrip(b,"*n"),$p(z,d,$tr(b,c))=c} q z
}

Changing $zstrip() to a $tr() saves one more byte

ClassMethod Order(s As %String) As %String
{
	s d=" ",z="" f i=1:1:$l(s,d){s b=$p(s,d,i),c=$tr(b,1E20/17),$p(z,d,$tr(b,c))=c} q z
}

So I end up with 86 bytes

and this is an updated version

ClassMethod Order(s as %String) As %String
{
	s d=" ",z="" f i=1:1:$l(s,d) s b=$p(s,d,i),c=$zstrip(b,"*n"),$p(z,d,$tr(b,c))=c
	q z
}

I do not work with Ensemble nor do I have Ensemble installed... But you could take a close look on that Ens_Enterprise_MsgBank.MessageHeader class, and check, if there is a mapping into an other, possibly readonly, database. Maybe somebody with ENS experience has a solution for you

As I learned the hard way, abstract classes do not have storage implementation, hence no indices either

One of the possible solutions

/// You can change the s:b]"" to an comma if there is always exact one space between the words
/// and remove the ,1) from $lts() if all word are numbered from 1..N with no number missing
ClassMethod WordOrder(s)
{
    s z="" f i=1:1:$l(s," ") s b=$p(s," ",i) s:b]"" $li(z,$zstrip(b,"*ap"))=$zstrip(b,"*n")
    q $lts(z," ",1)
}

This is a working solution and maybe not the shortest

I never had this kind of problem, but a quick and dirty method would be: 1) remove the 'Mount Read-only' flag, 2) run the tune table utility, 3) reenable the 'Mount Read-only flag'.  I hope, you do not have some mean application, waiting for the chance of his life, to get a writable database...

You can it enter via terminal, no question about, but it's a little bit cumbersome

// create the class
s cls=##class(%Dictionary.ClassDefinition).%New()
s cls.ProcedureBlock=1
s cls.Super="%RegisteredObject"
s cls.Name="ObjectScript.RightTriangle"

// add one method
s mth=##class(%Dictionary.MethodDefinition).%New()
s mth.Name="Main"
s mth.Description="Compute area and hypotenuse of a right triangle"
d mth.Implementation.WriteLine($c(9)_"write !,""Compute the area and hypotenuse of a right triangle"",")
d mth.Implementation.Write($c(9,9)_"!,""given the lengths of its two sides.""")
d cls.Methods.Insert(mth)

// add one more method
s mth=##class(%Dictionary.MethodDefinition).%New()
s mth.Name="Area",mth.Description="Area, computed from sides 'a' and 'b'"
s mth.FormalSpec="a,b"
d mth.Implementation.WriteLine($c(9)_"quit a*b/2")
d cls.Methods.Insert(mth)

// save the class (it's NOT compiled!)
w cls.%Save()

As you may see, creating a class via an IDE is simpler... but yes, in an emergency case you can do it also via a console access

First, ##class(%PopulateUtils).StringMin(16,16)    generates random printable chars for testing (as replacement for user input) and is not ment to be used to generate cryptographic random chars. If you need cryptographic random chars, use $system.Encryption.GenCryptRand(length). This is just a hint and is not a reason for your current problem.

Second, despite my very limited C# experience, there is one thing in your code, I do not understand. If the initial vector (IV) is used, then it should be used (for enryption and decryption) the same IV on both sides, but you create an IV on Cache side (with the populate utils) and an other one on the C# side: byte[] IV = new byte[16]; (new Random()).NextBytes(IV);

That your decryption can't work.

To have a successful comunication, agree with the other party on
- a passphrase (the key), padding is done inside the encoding function 
- an IV (or left it empty on both sides)
- and on how the data will be sent:  either as the encoded (binary) data or as a readable (base64) data.ISC's implementation of AESCBCEncrtypt/Decrypt works well. One of my application uses it to communicate with an Windows application written in Delphi, without any problem since more the 15 years (we do not use the IV). So your problem will be some kind of a home-made problem:
- not using the same keys on both sides
- applying some kind of transformation (utf-8, base64, etc.)
- something suchlike

I understand your answer (#2) the way as this is a one time job. The simplest and quickest way to do this is:

- disable all indices (comment them out),
- compile the class or classes
- do the bulk insert
- enable all indices (by removing comment markers)
- compile the class or classes
- rebuild the indices

Class My.Class
{
    /*  disable all indices
    index1 someindex1 on someprop1;
    index2 someindex2 on someprop2;
    */
}

The problem has nothing in common with Cache or IRIS, it's an OS setting. If a network drive is not available (for example the target is switched off), Windows waits an half an eternity.

You have to ask your sysadmin or Google, providing your Windows version. The very first hit I found is this but it's somewhat old.

Nice, merely your insert rate is somewhat low. About ten years ago, Cache inserted in proof-of-concept project  112000 rows per second. Seen in this way, the  (708000/20) 35400 are a bit little... 

REST-API is not my daily bread, so show me a few lines of your (problematic) code and I will try my best