ztta/roll_area: Roll Area
This parameter is used to specify the total size of the roll area, in bytes.
A part of this area (in the graphic, roll area 1) is allocated a user context at the beginning. Its size is defined in
ztta/roll_first. The partial area is for the data that must be contained in the roll area. During a user context change, this data is "rolled" (copied) into and out of a work process. If ztta/roll_area is larger than ztta/roll_first, the additional space makes a second part available (roll area 2).If the user context cannot be allocated more extended memory, this second part of the roll area is available for the dialog processes (see
Allocating Memory for User Contexts).By specifying a higher value for ztta/roll_area than for ztta/roll_first, you avoid allocating local private memory as soon as the set limits of the SAP extended memory are reached. The remaining roll memory therefore serves as the last buffer before a user context has to allocate heap memory.
This pushes back the point in time at which a work process is switched to PRIV mode (see
Private Memory). Although there advantages to this procedure, there are also the following disadvantages: The copying procedure is much slower for storing data in the roll area for changing work process contexts. The copy necessary for the roll area during context changes is slower than the allocation procedure used for the context change with SAP extended memory. Therefore, increasing the roll area memory slows down the context change.Goal:
Reduce data transfer to a minimum using copy procedures during context changes (value closer to ztta/roll_first), higher values avoid problems however (address space, swap space, operating system paging, work process change to PRIV mode, if the SAP extended memory limit is reached).
