Resource usage logging means the writing of resource data as rows to one or more of the resource usage database tables. The tables are named DBC.ResUsagexxxx, where xxxx is the name of the resource usage table (for example, SPMA, IPMA, and so on) as listed in Types of Resource Usage Tables.
The shorter the logging period, the more frequently data is logged, and the more disk space is used.
When the system is so busy that the resource usage table logging gets backed up, RSS will automatically double the logging period which effectively summarizes the data by providing values for a time period twice that provided by the previous logging period.
If you see the resource usage logging rates change without user intervention, this means that the database is busy. When no longer busy, the system resumes logging as before.