What is maximum size of a database in mysql?

The effective maximum table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits. The following table lists some examples of operating system file-size limits. This is only a rough guide and is not intended to be definitive. For the most up-to-date information, be sure to check the documentation specific to your operating system.
Operating System    File-size Limit
Win32 w/ FAT/FAT32    2GB/4GB
Win32 w/ NTFS            2TB (possibly larger)
Linux 2.2-Intel 32-bit    2GB (LFS: 4GB)
Linux 2.4+            (using ext3 file system) 4TB
Solaris 9/10            16TB
Mac OS X w/ HFS+    2TB