wdisp/shm_attach_mode is a SAP Parameter attribute which is used to control Shared memory attach and creation mode for SAP Web Dispatcher 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 determines what should happen to the shared memories of
the SAP Web Dispatcher. The possible values and their meanings
correspond to the values of the start option -shm_attach_mode of the SAP
Web Dispatcher. If the command line option is set explicitly to a
different value when the Web Dispatcher is started, this value is
definitive and the parameter value is overwritten.
Values for wdisp/shm_attach_mode ,,The shared memory is cleaned up and the SAP Web Dispatcher terminates. The behavior is the same as with the option –cleanup. The SAP Web Dispatcher connects to the existing shared memory (attach). If it does not exist, ,,the SAP Web Dispatcher ends with an error. Not useful The SAP Web Dispatcher creates a new shared memory. If this exists already, the SAP Web Dispatcher ends with an error. If a shared memory exists already, it is deleted. A new shared memory is then created. The Web Dispatcher attempts to attach itself to an existing shared memory. If a shared memory does not exist, a new one is created. This is also the default value, that is, SAP Web Dispatcher behaves like this if the options -shm_attach_mode <(><<)>mode> and -cleanup are not used, and the parameter wdisp/shm_attach_mode is not explicitly set to another value. As 5
See SAP Parameter Documentation for full SAP documentation for this profile parameter.