Outlook data files (OST and PST) size issues:

Outlook is the most commonly used Email client in business domain. Various versions of Outlook had been emerged till date. The latest among the Outlook versions is Outlook 2013. ANSI file format was supported by the Outlook 2002 and earlier versions. The later versions of Outlook support Unicode format. The ANSI file format doesn't support maximum file size above 2 GB. That why the Outlook 2002 and earlier versions have a 2 GB size limitation for the OST/PST files. Whenever the file size reaches the size of 2 GB, Outlook can't work perform properly. And later on the data files may get severely corrupt.

Microsoft provides inbuilt free utilites to handle the OST/PST file size and corruption issues.
User can use the PST2GB tool to truncate a PST file that is more than 2 GB in size. Scanpst.exe and Scanost.exe can be used to repair a corrupted .pst and .ost file respectively and to fix other file corruption issues.
          
Default maximum OST/PST file size:
Outlook 2002 and earlier versions            2 GB
Outlook 2003 and 2007                             20 GB
Outlook 2010                                             50 GB

The OST and PST file size can be modified by changing following the registry entries:

• The MaxFileSize registry entry
• The WarnFileSize registry entry
• The MaxLargeFileSize registry entry
• The WarnLargeFileSize registry entry

MaxLargeFileSize DWORD registry value can be modified if the user wants to extend the deafault maximum file size.

Location of  MaxLargeFileSize DWORD registry:

You can configure the Outlook OST/PST file size limits simply by changing the registry values.

But, while modifying the registry, the user must take special care as, if its some incorrect changes will be done to the registry, it can lead to severe data loss situations. 

So, before modifying the registry, it’s better to backup the registry. So that, if something goes wrong while modifying the registry then you can restore the registry from the backup. Read my upcoming article, if want to know more about registry backup and restoration procedure.