Roll and Paging Buffers, Extended Memory

Definition

The roll and paging buffers are the preferred working area of the roll and paging areas for an instance (application server). The remaining area is located on disk as roll and paging files. The user context is stored in the extended memory and the roll area (when the job is "rolled out" of a work process). The paging area stores special data for the ABAP processor, while the extended memory stores a large portion of the internal tables of a program.

You set the roll and paging buffers, as well as the extended memory using the parameters in the instance profile.

Repository Buffers (Nametab Buffers)

Definition

The name table (nametab) contains the table and field definitions that are activated in the SAP System. An entry is made in the Repository buffer when a mass activator or a user (using the ABAP Dictionary, Transaction SE11) requests to activate a table. The corresponding name table is then generated from the information that is managed in the Repository.

The Repository buffer is mainly known as the nametab buffer (NTAB), but it is also known as the ABAP Dictionary buffer.

The description of a table in the Repository is distributed among several tables (for field definition, data element definition and domain definition). This information is summarized in the name table. The name table is saved in the following database tables:

• DDNTT (table definitions)

• DDNTF (field descriptions)

The Repository buffer consists of four buffers in shared memory, one for each of the following:

Table definitions	TTAB buffer	Table DDNTT
Field descriptions	FTAB buffer	Table DDNTF
Initial record layouts	IREC buffer	Contains the record layout initialized depending on the field type
Short Nametab	SNTAB buffer	A short summary of TTAB and FTAB buffers

The Short nametab and Initial record layouts are not saved in the database. Instead, they are derived from the contents of tables DDNTT and DDNTF.

When access to a table is requested, the database access agent embedded in each work process first reads the Short nametab buffer for information about the table. If the information is insufficient (for example, the SELECT statement uses a non-primary key) it accesses the Table definitions buffer and then the Field descriptions buffer. By reading the Repository buffers, the database access agent knows whether the table is buffered or not. Using this information, it accesses the table buffers (partial buffer or generic buffer) or the database.

The IREC buffer is read:

• When a
REFRESH command is executed in an ABAP program

• At an
INSERT command, when a record is created in the buffers before the data is inserted and the fields are initialized with the values found in IREC buffer

Buffer Types

finition

There are seven main groups of buffers found in the shared memory. For more information on each buffer type, see :

Repository Buffers

Table Buffers

Program Buffer

SAPgui Buffers

Roll and Paging Buffers

SAP Calendar Buffer

SAP Cursor Cache

Displaying Detailed Work Process Information

Procedure

1. Choose CCMS ® Control/monitoring ® Work process overview. Alternatively, call Transaction SM66.
2. Position the cursor on the instance and choose Choose. You can terminate the program that is currently running and debug it.

For background processes, additional information is available for the background job that is currently running. You can only display this information, if you are logged onto the instance where the job is running, or if you choose Settings and deselect Display only abbreviated information, avoid RFC. In any case, the job must still be running.

Monitoring Servers and Work Processes

Use

When an operation mode has been switched, you can see in the process overview whether the work process types have been changed correctly.

Procedure

To monitor the work processes on your current application server:

From the R/3 initial screen, choose Tools ® Administration ® Monitor ® System monitoring ® Process overview. Alternatively, call Transaction SM50.

The system displays an overview of the work processes for the server you have logged onto.

The information for each work process is displayed in a line. The Ty. column shows the work process type: for example, DIA is a dialog process, BTC is a background process.

To monitor the work processes on a different application server:

From the R/3 initial screen, choose Tools ® Administration ® Monitor ® System monitoring ® Servers. Alternatively, call Transaction SM51.

The system displays a list of the R/3 servers. To display the processes for a particular server, position the cursor on the line containing the server name, then choose Processes.