em/max_dump_lines is a SAP Parameter attribute which is used to control Maximum number of memory lines written to mm.dump 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 .
Maximum number of lines in the mm.dump diagnosis file. This value is set
by SAP Support for analysis.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.