What is GUID format

Morning everyone
Maybe I am showing my ignorance - but then that's nothing new.
I am involved in a brand new project and have been told that a parameter is going to be passed to the as400 in GUID format.
I am googling "GUID format AS400" and even though its mentioned all over the place, I am having trouble in locating how to store this data (maximum size etc. ) on the as400 as this parameter will be needed elsewhere.
If anyone can help, it would be MUCH appreciated

Alan Shore
Programmer/Analyst, Direct Response
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"If you're going through Hell, keep going" - Winston Churchill


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