abap/pxa is a SAP Parameter attribute which is used to control Mode of Operation of Program 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 .
DParameter influences behavior of program buffer It can have following values: shared program buffer is used by all work processes; default, cannot be changed gen_local ABAP programs are generated in user LUW gen_local_in_dialog ABAP programs are generated in dialog processes within the user LUW and in other processes within their own LUW. gen_remote where possible, ABAP programs are always generated in their own LUW; default value protect program buffer is protected from being overwritten; this addition only has an effect on NT, HP-UNIX und SOLARIS use_semaphore semaphores are used to lock the program buffer; default on NT use_mutex mutexes are used to lock the program buffers; default on all other platforms develop as a rule, a database commit is triggered after an ABAP program is generated. Because this additional database commit influences the behavior of an application, the addition cannot be used in a productive system. In a development system, this additional reduces the likelihood of database deadlocks. generate This addition ensures that ABAP programs are, as a rule, generated only before they are used. For diagnostic purposes only. source ABAP sources are also loaded into the program buffer.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.