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Facing error while upgrading from 1.8.12 to 1.8.14 during upgrade process
Updating Database
Performing necessary upgrade queries...
Language mysubslang (/home1/oraerpco/public_html/inc/languages/mysubslang) is not installed

"mysubslang" isn't a core language file, it must belong to a plugin (possily called "MySubs"). You need to upload that language file.

Looks like that would probably be related to MySubscriptions plugin if you haven't managed to solve this.

The best thing to do is to use the setting to disable all plugins when you are going to do an update because then plugin files will not be loaded which can cause problems.