if you need add a string, you should concatenate it with operator _

+ converts all types to number, and doing arithmetical operator add

7_"" became "7"
+"5apples" became 5

Both of this are completely different products. Where: Ensemble is an Integration platform, and DeepSee is an Business Intelligence

Also, you can look at some learning courses from InterSystems, about Ensemble and DeepSee and Caché 

because + is an operation for numbers, and yes, answer is correct, because 5 + 7 is 12

if you expected to see "5apples7 orange", in this case you should use concatenate operator "_"
write "5apples" _ "7 orange"

What do you mean by dynamic sessions ?
Web sessions in Caché only two types, preserve or not. Preserve just keep working in the same process, for all request in this session, and keeps every locks. By default sessions, instead, only keeps data in %session.Data, and release locks after end of request.

Unfortunately in times when web-applications prevail other types of applications this approach is cannot be widely used. This way can't be used directly in CSP, because of by default any session could be joined to any process, but Procces-private globals is not session-provite globals. And If you need to have such functionality with CSP, you should use Preserve sessions or use something like Sessions-private global, something like this

^CacheTemp.SomeTableD($select($isobject($get(%session)):%session.SessionId,1:$job))

Good article, but unfortunately I don't see the answer for last part for the question "How can I minimize the phenomena?"

So, in my practise, such behavior, in most cases related with some application's buffer globals, or logging globals. And mostly  we don't need in this journal, because it is not important part of our data, and we should not spend important resources for doing this. And we can cut off journalling for such globals. There are some ways to do it: 

• Remap such globals to another database with disabled journaling. But this way has some exceptions, any changes in transactions, should be journaled in any way.
• Use ENABLE^%NOJRN to disable journaling non-transact changes, and return back with DISABLE^%NORJN.
• Remap to database CACHETEMP, which disabled for all changes, even in transaction.

WRC

As you have not showed full example of your code, I suggest that you use wrong class for fileStream.

For any text's you should use Character's stream, such as %Stream.FileCharacter, %Stream.GlobalCharacter

All replacements for different $zu you can find here

so, in case with $zu(49), you can get such information with class SYS.Database, and it's not delimited now, and has properties

In this case, for $match you should define regex which match full given string, so it could looks like

write $Match("Find String ABC",".*(abc|ABC).*")
1

or you can use $locate, which returns position for first matched string

write $locate("Find String ABC","abc|ABC")>0
1

What do you mean, can you give some examples ?

Sure, thats needs because this variable should be available in any place for this process, just because this code executes in context where works any output commands like write

I would recommend regexr.com and regex101.com as a tools for testing regular expressions, this tools a bit simpler, but works online and cost nothing.

You have two cases, you change storage definition or you can use calculated value. But in case with calculated value, you have two options. It's an object's access and sql access, and such getter it is just only for object's access. For SQL you should define SqlComputeCode. Something like this.

Property Invalid As %Library.Boolean [Calculated, SqlComputed, SqlComputeCode = { s {*}={+$G(^GLOBAL({Code},"INVALID"))} }];

more details in documentation

$zhex
hex to dec

write $zhex("99")
​153

and back, dec to hex

write $zhex(153)
​99

be careful, hexadecimal should be a string and decimal should be a number