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Background documentation Memory Requirement of the SAP Web Dispatcher Locate the document in its SAP Library structure

The SAP Web dispatcher must reserve as much memory as possible to store large tables.

Server Tables

The server tables contain the configuration values from the three files, info.icr, groups.icr, and urlprefix.icr (or fetched from the application servers).

The following formula estimates roughly how much memory is required:

Memory requirement  = (S × NS + G × NG + U × NU) × 2 Bytes

The letters have the following meaning:

Variable

Parameter Value

Default Value

S

wdisp/max_servers

128

NS

wdisp/max_server_name_len

64

G

wdisp/max_server_groups

128

NG

wdisp/max_server_group_name_len

20

U

wdisp/max_url_map_entries

300

NU

wdisp/max_url_map_path_len

256

For the default settings this comes to 87552 bytes, which is negligible.

Session ID Table

In this table each SAP Web dispatcher keeps to the server names of the active sessions, provided that the dispatcher is working with external session IDs or J2EE session IDs. The algorithms are described under Determining the Server Group. Information about the associated profile parameters can be found under Parameter Settings for Session Dispatching.

The memory consumption of the table depends on the maximum number of entries (parameter wdisp/HTTP/max_session_tab_entries as well as the use of unicode.

Memory Requirement of the Session ID Table

Maximum number of entries

Memory Requirement ASCII

Memory Requirement Unicode

10000

1.7 MB

2.0 MB

50000 (default)

8.5 MB

9.7 MB

100000

17.0 MB

20.1 MB

 

MPI Parameters

The MPI memory is a pure communication memory. This means the Web dispatcher reads the data from a partner into this memory and then forwards this data to another partner. Once the data has been forwarded the memory is free again. The whole MPI memory (mpi/total_size_MB) is split into blocks of a fixed size of the value of mpi/buffer_size. The standard value of mpi/total_size_MB is 80 (megabytes). The standard value of mpi/buffer_size is 65536 (bytes).

IP Mapping Tables for Stateful SSL Connections

The SSL client IP table is needed for end-to-end SSL and contains the mapping of client IP to the application server:

The section Profile Parameters of the SAP Web Dispatcher contains further information about the parameter wdisp/HTTPS/max_client_ip_entries, and a table containing examples of the memory required for certain settings.

 

 

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