rsdb/otr/buffersize_kb is a SAP Parameter attribute which is used to control Size of Online Text Repository Buffer [kB] 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 .
This parameter defines the size of the Online Text Repository buffer in
KB. The buffer buffers texts that are managed in the Online Repository.
If the buffer is full, texts that are not referenced are suppressed. If
this is not possible, the text cannot be buffered.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.