Specifying maximum size of activity attachments
Although you can specify the maximum file size of activity attachments that can be stored in the database, the absolute maximum size is determined by many factors (for example, the maximum size of your database server). In most cases, specifying a small activity attachment size limit (for example, 500 for a 500 KB file) should be large enough. The maximum file size for a Word document, for example, is 32 MB.
Note: Do not increase this value until you have verified through testing that performance of your system remains acceptable at the new value. Storing a large number of attachments will increase the size of your database very rapidly, affecting backup requirements and the available disk space on your database server.