The initial amount of memory the server uses for holding table data, network buffers, cached download data, and other structures
used for synchronization. When the server has more data than can be held in this memory pool, the data is swapped to disk.
Swapping data to disk results in a significant performance penalty.
The size is the amount of memory to reserve in bytes. Use k, m, or g to specify units of kilobytes, megabytes, or gigabytes, respectively. If no letter follows the number, the size is in bytes.
The unit p is a percentage either of the physical system memory, or of the process addressable space, whichever is lower. The maximum
process addressable space depends on the operating system. For example:
2.5 GB for Windows 32-bit Advanced Server, Enterprise Server and Datacenter Server
3.5 GB for the 32-bit database server running on Windows x64 Edition
1.5 GB on all other 32-bit systems
On 64-bit database servers, the cache size can be considered unlimited