UltraEdit handles files up to and over 4GB. UltraEdit is disk-based. This means it only loads small portions of the file at once into memory so it does not use all the memory and stop other applications from running. However, it does make a temporary copy of the file to achieve this and this can take time for large files.
There are two options in the Advanced menu and Configuration to consider.
1) Disable line numbers - Check this to disable the line numbers on large files, it makes navigation a lot quicker. This may be set in the Miscellaneous topic under the Editor Display branch in Configuration in the Advanced menu.
2) Open file without temp file - This instructs UltraEdit not to create a temporary copy of the file. This does however mean it is editing the original file so any changes are permanent. Several users make use of this for large files. You can set a threshold for this so that it only happens on files over a certain size. This may be set in the Temporary Files topic under the File Handling branch in Configuration in the Advanced menu.
Additionally, you may want to disable automatic conversion from Unix to DOS in configuration if it is enabled also.