Error when attempting Merge with output set to network server .gdb

[DylanMurphy]

I am getting this error: 

ERROR 999999: Something unexpected caused the tool to fail. Contact Esri Technical Support (http://esriurl.com/support) to Report a Bug, and refer to the error help for potential solutions or workarounds.
FDO error: -2
FDO error: -2 ['output_name']
Failed to execute (Merge). 

when attempting to run Merge on several very large shapefiles with the output destination set to a .gdb on an external server connected as a network drive. I need the output on this server as this is the registered Data Store for my organization's Portal. The strange thing is that the tool runs until the progress bar is at nearly 100% before failing, and after the failure, the output feature class still shows up in the .gdb. When I add this Merge output to the map, though, some sections of the data are missing.

The Merge executes successfully and without any of these issues when the output destination is set to the local project geodatabase.

Currently, my workaround is to run the Merge to the project geodatabase on my machine, then copy the data over to the final destination on the server, but this is costly time-wise due to the size of the merged data (many GB) and is not ideal as a long term solution. 

Has anyone else encountered this? Any ideas on why I might be getting this error when output is set to a geodatabase located on a network server? 

[DanPatterson]

although not ideal, have you tried converting the shapefiles to local featureclasses in a gdb, then merge to your destination gdb?  Featureclasses might solve some problems leaving the last step of writing to your destination gdb (ie. non-local) the final step

[DylanMurphy]

Hi Dan, thanks for the reply.

I will give that a shot, and if it works it will tell me the issue is stemming from the use of shapefiles, which will be helpful.

However, you're right that it wouldn't be ideal, in that it is essentially the mirror process of my current workaround of merging to local gdb then copying to the destination gdb on the server. Both processes involve writing an FC as an additional step to the merge, which adds a lot of processing time due to the size of these feature classes (tens of millions of polygons).

Maybe one will be faster than the other, though. I will report back once I try this out.