January 24, 2013 at 9:15 am
So I'm curious, I see various articles and posts suggesting or recommending the use of various "undocumented" commands / flags. What I'm wondering is, if these are "undocumented," how do people determine what they do, what the options are, etc?
Things like dbo.xp_delete_file, or trace flag 2537 (as mentioned in Day 19 of the 31 days of DR[/url])
Is it just a "try it and see what happens" sort of thing, or are these things found out in conversation with MS devs...
Obviously, if something is "undocumented" outside of MS (xp_delete_file) it's likely (I would think) either because it's dangerous to use (hmm, lets run "exec master.dbo.xp_delete_file 0, 'c:\',N'*',NULL" and see what happens...) or not considered useful for 99.9% of situations.
As I said, just curious.
Jason
January 24, 2013 at 9:24 am
Undocumented means just that, it's not listed in the official documentation (BoL). Some things are mentioned in kb articles, some in discussions with MS engineers or devs. Some can be worked out without any MS interaction (debugger or similar).
The xps can be seen with queries against the database metadata, or reading through the code of system procedures or jobs created by SQL features.
Documenting a traceflag or procedure means that MS must subject it to the full bank of tests they do on SQL Server (a huge time and resource investment), must commit the resources to add it to the docs and cannot change or remove the traceflag without the 3-cycle deprecation policy kicking in
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
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