DISM commands. What am I missing?

ref: https://technet.microsoft.com/en-us/library/hh824869.aspx
To check if an image is repairable
1. Scan the image to check for corruption. This operation will take several minutes. For example, at a command prompt, type the following command:
Dism /Online /Cleanup-Image /ScanHealth

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2.  Check the image to see whether any corruption has been detected. For example, at a command prompt, type:
Dism /Online /Cleanup-Image /CheckHealth

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When you use the /CheckHealth argument, the DISM tool will report whether the image is healthy, repairable, or non-repairable. If the image is non-repairable, you should discard the image and start again. If the image is repairable, you can use the /RestoreHealth argument to repair the image.

The descriptions seem the same.
1. "to check for corruption"
2. "check the image to see whether any corruption has been detected"
I'm sorry if my English is TOO GOOD but these say exactly the same thing.

What I've always wondered is why would one not just go ahead and run /RestoreHealth and skip /scanhealth or /checkhealth?
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Fred MarshallPrincipalAsked:
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JohnBusiness Consultant (Owner)Commented:
ScanHealth takes longer


To your point, I no longer bother. If I think I need to run it at all, I just run RestoreHealth

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RaminTechnical AdvisorCommented:
/scanhealth and /checkhealth arguments can help you to decide if you need to use /RestoreHealth. I think /RestoreHealth itself  can cause problem if something go wrong during repairing (replacing).
JohnBusiness Consultant (Owner)Commented:
I have not had RestoreHealth go wrong during repairing unless the system is so badly broken it needs to be rebuilt.
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Fred MarshallPrincipalAuthor Commented:
Ramin:  Yes but I have to wonder "what is the difference?"
JohnBusiness Consultant (Owner)Commented:
If you read my link, the only difference is speed. Check apparently does less work than Scan but otherwise they are the same and really don't bother. Just run Restore when you need it.
RaminTechnical AdvisorCommented:
/CheckHealth  only check whether the image has been flagged as corrupted.

/ScanHealth   only scan the image for component store corruption. This option does not fix any corruption.

/RestoreHealth to scan the image for component store corruption, perform repair operations automatically, and records that corruption to the log file.  This generally takes 15-30 minutes depending on the corruption and size of the partition.

JohnBusiness Consultant (Owner)Commented:
You are somewhat duplicating the easy answers  . A summary of this has been already posted
Fred MarshallPrincipalAuthor Commented:
I'm sorry, my original question didn't actually ask the question I had hoped to ask: "what is the difference functionally?"  
i.e. How do the end results differ?

But, certainly, if we start with the hypothesis that they ARE THE SAME as the documentation suggests, then that one is faster is interesting and belies the conclusion that they are the same.
And, that there are two of them, that also suggests that they are not the same.

So, it appears that Scan must be doing something in addition to Check - and the question about functionality remains unanswered.

Here's a hypothesis:
"Scan does more than Check but we see the results of the difference so infrequently that we conclude they are the same as a practical matter."
I'd still like to know "what more?" as in "what difference?"  
If the answer has no  practical significance then at least we know with more certainty.

I believe that John Hurst has lots of experience with these tools.  Right?  So his observations over a large sample set is valuable.
Perhaps I should leave it there.

Oh! Now I see Ramin's response.  That makes sense to me.  I don't see anything in the documentation about flags.  Where did you get that Ramin?  I don't see any duplication.
JohnBusiness Consultant (Owner)Commented:
Your summary says what we said in brief . The only substantial difference is length of time. Otherwise the same. And my view based on a lot of personal experience is that you do not need to bother scanning. - just repair
Fred MarshallPrincipalAuthor Commented:
Ramin's reference also says this;
You can run scanhealth & restore health at the same time like this
DISM.exe /Online /Cleanup-image /Scanhealth && DISM.exe /Online /Cleanup-image /Restorehealth
So, as I understand it, one checks for flags and the other checks for corruption (more directly?)
[This is probably as clear as we're going to find I'd guess].

And, it says:
You can run Check, then Scan, but you should always run RESTORE HEALTH
Which is what John Hurst has suggested.

Good enough.
Fred MarshallPrincipalAuthor Commented:
Thank you both!
JohnBusiness Consultant (Owner)Commented:
You are very welcome and I am always happy to help you
RaminTechnical AdvisorCommented:
You're welcome, and thanks.
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