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====== Working with XROOTD ======

You can use space on XROOTD file servers which is visible from atlas16,18 and ascinode (test cluster).
Login to these computers and look at the directory:

<code>
/atlasfs/atlas/local/
</code>

You will see your name (likely). You can also have data directly deposited in a the same file system from a grid job by using the "--destSE=ANL-ATLAS-GRIDFTP1" for prun or pathena.  It will appear in the directory "/atlasfs/atlas/dq2/user/<yourname>" .  The subdirectory structure is detemined by the output dataset name.  You'll have to grope around a bit to find where the output went under this directory (some of the "."'s in the datset get transformed to "/").

To access files using root via xrootd on the worker nodes [this is true on ascinode but is it on 16 and 18?] you can use "xprep".  Let's say you ran a grid job and your data is now available in the following area:
<code>
/atlasfs/atlas/dq2/user/<yourname>/user.<yourname>.xxx/yyy.root
</code>
You can prepare the files for use with root in the following way 
You run the following xprep command to register it (note that "/atlasfs" is not in the name):

<code>
xprep -s aschead01 /atlas/dq2/user/<yourname>/user.<yourname>.xxx/yyy.root
</code>
Instead of doing this file by file you may provide a list of files with the "-f" option.

In root you can open the file as "root://aschead01///atlas/dq2/user/<yourname>/user.<yourname>.xxx/yyy.root".

To check that the files have been registered you can do the following command:

<code>
xrd aschead01 locatesingle /atlas/dq2/user/<yourname>/user.<yourname>.xxx/yyy.root
</code>