For editing very large documents (file size up to 300 MB), a special memory optimization is implemented on loading such a file so that the total memory allocated for the application is not exceeded. The minimum file size that enables this large file optimization can be configured with the option Optimize loading in the Text page for files over (MB) available from menu .
A temporary buffer file is created on disk so you have to make sure that the available free disk space is at least double the size of the large file that you want to edit. For example Oxygen can load a 200-MB file using a minimum memory setting of 512 MB and at least 400-MB free disk space.
The increase of the maximum size of editable files comes with the following restrictions:
The option Format and indent the document on open is disabled for non-XML documents. For XML documents, it is done optimizing the memory usage but without respecting the options set in the Format preferences page.