SharePoint store all the uploaded documents in the database. Having a restriction on the file upload size is always a good idea. You can do this two ways,
1. Give a upload file size limit under general setting of the web application in the central administration.
Upload size setting
2. Modify the metabase.xml file on the IIS server.
a. Before you can edit the metabase.xml file you must tell IIS to allow you to edit the file. In IIS, right click the name of the server and select properties. Check “Enable Direct Metabase Edit”.
IIS File Upload
b. Find the metabase.xml file located in C:\windows\sytem32\inetserv and open the file in Notepad.
c. Search for AspMaxRequestEntityAllowed and increase the value. The default value is 204800 (200K). Setting the value to 1000000 will allow 1 MB file uploads.
d. You may now wish to uncheck the IIS property called “Enable Direct Metabase Edit”.
To increase the file download size limit, repeat all steps above but in Step 3 find the parameter called AspBufferingLimit. The default download limit is 4MB.
Reference
Diganta Kumar is an experienced Technical Program Manager with a passion for technology. He has architected and developed software for over a decade for a broad range of industries. Diganta is a founder of two online IT businesses. He likes to help, mentor, and manage software development teams to improve and produce great software. He currently works as a Principal Program Manager for Microsoft. Before joining Microsoft, he was with AWS for five years, where he managed large cross-functional programs on a global scale.
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