I'm managing a SQL Server with reporting services running on it. The ReportServer database is getting too big. When I checked which table is occupying a lot of space, [ExecutionLogStorage] came up. I found out that the data stored in this log table can be manipulated by ExecutionLogDaysKept property. WHen I checked ConfigurationInfo, the property is set to -1. Is that the default value set when SSRS is installed? from what I read SSRS will only store 2 months worth of data in this table but I see data from 2011 which I suspect from when SSRS is installed. I would like to understand the significance of -1. If it's confirmed that it's incorrect I'll go ahead and set appropriate value for my environment.
The default is usually 60, which keeps about two months of data.
Setting the value to -1 will keep the data 'forever', as you are finding (if you delete a report, log data for it is also dropped).
Setting the value to 0 does not keep any data - there are some references out there that INCORRECTLY tell you that setting a value of 0 has the effect that -1 actually does (don't ask me how I know...).
I like to set this to 400 - that way you have over a year's worth of data, which can be handy if you want to do analysis over time. Also, you will pick up reports that only run annually, if that's a concern.
Most installations change enough in a year that there's not much point to keeping more data.