Merge & Append: Partial output generated

[jblng]

I am trying to merge two separate datasets (shapefiles) which each have about 4 million features each. Each one is in a different UTMZ (32N and 33N) and do not intersect because they are supposed to be combined to fit the entire area of interest.

I have tried both merge and append to combine these two datasets, however both times the outputs only produce about 24k additional features to the first dataset that gets read in, even though there is no warning or error message. The merged features are geographically dispersed across the AOI and geographically seem to line up with the original dataset

Should I reproject to GCS and then try merging? Simply merging takes ~7 hours, so I wanted to try other things before taking that step. Otherwise, would it be recommended to import them into a GDB?

Any advice would be greatly appreciated, and happy to clarify the issue more. thanks! 

[JayantaPoddar]

The issue could be with the size limit of shapefile. But again, it's wise not the force the data (of multiple UTM Zones) to a single UTM zone.

Here is my suggested steps.

1. Create a File Geodatabase.

2. Using Project tool, reproject one of the inputs to GCS_WGS_84. Save the output as a Feature Class in the above File GDB.

3. Use Append for to integrate the second layer to the Feature Class. Change Schema_Type to "NO TEST", if the schema doesn't match.

[jblng]

Thanks Jayanta - I followed these steps but now the second, appended layer (33N) nearly replaced the original (32N) layer that was projected in step 2. The total is still around 4.4million rather than the expected 8-9million features. Are there also size limits in file geodatabases as well?