There are two places where there is a setting.
One is in CSA, but you are not likely to have access to CSA on ondemand
The other is in Administration in system options
.have not set it in mys sytem.
Once with the limit set to 20 Mb the work around was to split the file into 20 Mb pieces.
The 20 Mb recommendation applies to your version as well. My screenshots are from a system which was initially installed as r8.1 and at the time there was no default. If there is a default then it comes from a fresh install of a later version. upgrades