I don't have any information on the 12c version of Sys Admin yet, but I can tell you that the essentials exam is going to be focused more on implementation skills. I know I haven't given you very much information, but maybe enough to let you know if you should take the 12c Essentials or wait for the 12c Sys Admin. There will likely be a single exam upgrade path to the newest version when the 12c Sys Admin is released, if you wanted to go ahead and pursue 11g. I wish I had more concrete information for you.
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