rsdb/esm/mutex_n is a SAP Parameter attribute which is used to control Number of mutexes in ESM-Buffer information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
Specifies the number of mutexes that are used for synchronization in the
ESM buffer. If the value is too small, the level of parallelism can
drop. If the value is too high, too much memory space is used. If the
value is zero, a value is chosen that allows the greatest possible level
of parallelism (with an increased memory requirement).
See SAP Parameter Documentation for full SAP documentation for this profile parameter.