Reads or sets counters for MiniVoicemail message.
The operation is atomic and the counter is locked while changing the value. The counters are stored as text files in the minivm account directories. It might be better to use realtime functions if you are using a database to operate your Asterisk.
account- If account is given and it exists, the counter is specific for the account.
If account is a domain and the domain directory exists, counters are specific for a domain.
name- The name of the counter is a string, up to 10 characters.
operand- The counters never goes below zero. Valid operands for changing the value of a counter when assigning a value are:
i- Increment by value.
d- Decrement by value.
s- Set to value.
This documentation was imported from Asterisk Version SVN-branch-1.8-r379342