I was just expanding on Joshua's observation about changing datasources instead of creating lyr files from scratch. I know in the upgrade from 10.3.1 to 10.5.1 for my org we had to rebuild certain objects from scratch as they either crashed completely or performed very poorly in 10.5.1 unless created brand new. I guess the lesson there for ESRI software is to rebuild objects at some frequency (maybe every 2-3 years especially if going through an upgrade) to keep objects working at peak performance.
- created a new .lyr file in ArcMap 10.4 and save it as .lyr file pointing to SDE SQL 10.4. Same result, slow
- created a file geodatabase and copied to a feature dataset with layers used by the .lyr files. and point .lyr file to layer in FGDB. It runs fast, as it was running in SDE Oracle.
Conclusion: .lyr files that point to SDE SQL databases are slower than these same .lyr files pointing to SDE Oracle or FGDB.
