BASIS SUPPORT

SAP APPLICATION SERVER

Application Server Flow:
1. The User Submit the Request using SAP GUI using Application Server Host Name and Instance Number (Port).
Port Number is derived from a two Digit Instance Number where SAP Application Server is installed.
Instance (Application Server) Number is a two Digit ID which ranges between 00-99(where 97(Diagnostic Agent, 98(Solution Manager Diagnostic) and 99(SAP Router) are reserved by SAP).
The Host Names and Ports are resolved from /etc/hosts and /etc/services. Most of the Companies Uses DNS Server for Host Name and Service Resolution.
DIAG (TCP/IP) Stands for Dynamic Information Action Gateway is an SAP Specific Protocol to communicate with Application Servers.
2.The User Submit the request using a supported Browser(IE, Mozilla) to access the system using SAP GUI for HTML or Net weaver Business Client or Business Client 6.0
Hostname should be a Fully Qualified Host Name derived from the parameter icm/host_name_full
Port Number is defined by the parameter icm/server_port_0=PROT=HTTP,PORT=8000 .These parameters are maintained using RZ10
Note: Change in Parameters Requires Instance Restart.
These details can be obtained from SMICM–>Menu Go to –>Services
3.The Classic GUI(win, java) Requests are received by the ABAP Dispatcher and Kept in the wait queue
4.The Web Requests that are sent by the browsers are received by WEB Dispatcher (If Configured) Else Received by Internet Communication Manager(ICM) which can be seen from Transaction SMICM.
The Users can be displayed by using SM04 with login(session) type”PLUG-in HTTP” or simply “HTTP”
The Users are displayed with Status “GUI” when login using Classic GUI.
The Users are displayed with Status “RFC” when login from other Instances
5.SAP ABAP Dispatcher maintains the Work Processes and identifies the Load handled by Work Processes.
6.The Dispatcher allocates a freely available process to the User Request based on FIFO(First-in First-out).
6a.The Work Process Rolls-in the User Request into WP Task handler.
7.The Work Process Contains Inbuilt Task Handlers to Interpret the Request
8.The Screen in the User request is Interpreted by Screen Handler
9.The Programming Language in the User request is Interpreted by ABAP Handler
10.The SQL Scripts(commands) in the User request are Interpreted by SQL Handler
SAP Uses “Open SQL” Language in the SAP Programs. This Open SQL is Independent of all the databases.
Open SQL is Converted into Native SQL with the Help of DB Client while Connecting to Database.
The Database Connection requires a Hostname, Port, and Protocol
0-65535 TCP/IP SQL(SEQUEL)
Port Protocol Language
Oracle 1521-1529 Net8 PL/SQL
SQL Server 1433 Named Pipes T-SQL(Transact-SQL)
IBM DB2 5912 tcp/ip SQL/PL
Sybase 4901 tcp/ip T-SQL(Transact-SQL)
MAXDB 7210 tcp/ip mysql
HANADB 3nn15 SQLDBC SQLSCRIPT
(NN is instance no)
The SAP Work Processes using DB Client and SAP OS/DB Specific Kernel and Communicates with Database using above specific port and protocols.
11.R3 Buffer is used to store the most frequently used Content and Less Frequently Modified(updated) Content based on Technical Settings in SE13 and parameters in RZ10.
12.if the Response is not available in R3 Buffer then the Process goes to the Database using DB Specific Client and SAP Kernel(OS and DB Specific)
13.Database Provides the response to the SAP Work Process after necessary Interpretations.
14.The SAP Work Process Checks whether the Content is eligible for buffering, so that a copy can be kept in R3 Buffer for handling Similar Requests in future.(These Buffers are accessed by all the Users who log-in to the Application Server)
15. The Work Process roll out the User Related information into User Context.
User Context: it is a small memory Area where the User Related information is stored.it contains user Authorizations, parameters, common user attributes etc.. it is lost when the user is logged out. it is specific to User only.
R3 Buffer builds when the Instance(Application Server) is started and R3 buffer is lost when the Application Server is Stopped
16.The Response is sent to User.
Roll-in: it is the Process of Copying the User Context into WP Task Handler. When User is logging for the first time the Roll-in is not available.
Roll-out: it is the Process of Copying the User-Specific Information into User Context while sending the Response to the User by a Process.
The User Context is displayed using transaction SU56
The Components of Application Server
1.Application Server Dispatcher
2.Dispatcher Wait Queue
3.Work Processes and Task handlers
4.User Context
5.R3 Buffer
6.DB Client
7.SAP Kernel
Dispatcher: Each Application Server(Instance) contains one dispatcher. it handles the User requests and roue the request to the work processes based on FIFO(First-in First-out).
it is displayed using SAP MMC(Microsoft Management Console), SAP MC SAP Management Console(java applet based),dpmon and SM51.
The dispatcher(instance)/Application Server is started by using command “startsap r3” and stopped by using command “stopsap r3”.
SAP MMC is available on Microsoft Windows Servers.
SAP MC is a Java-based tool used to start and stop the Instance using web browsers.The URL http://hostname:50013/
SAPMMC.SAR file is also provided in the Netweaver 7.5 version to monitor the Application Servers(Dispatchers)
dpmon: Dispatcher Monitor is applicable to both Unix and Windows Servers.
it provides the dispatcher details.
login as <SID>ADM and type dpmon. if a specific Instance dpmon is required then dpmon pf=<instance profile>
$su – sidadm
$cdpro (change directory to Profiles)
displays the list of profiles.
dpmon will be used to kill the expensive processes that are running for longer time.it is also used to kill the processes that are in private mode occupying the entire memory of the system.
if the system is further congested there is no other option except to power off/on the system.
Dispatcher wait Queue:
Dispatcher Queue Statistics are displayed by dpmon,sapmmc and sapmc.As this is the Queue they are not displayed through any transaction in SAP.
dpmon–>menu–Request Queue Statistics–> it displays the number of users in the Queue.
dpmon is used to monitor the statuses of work processes using the option P for the list of work processes and option ‘L’ for a long list.
if the PID is known the Process can be killed at OS level using option
kill -9 PID to free the resources.
Note: Configure the Memory parameters so that SAP system should not be a bottle neck on the Operating System.
An SM51 transaction is used to display the list of Application Servers/ Instances/ Dispatchers.
Starting and Stopping of SAP System(Application Servers)
Login as <sid>adm
#startsap r3 start sap system
#stopsap r3 stop sap system
Use Microsoft Management Console/SAP Management Console and select the System(Use Administrator Credentials)–>right Click Start/stop the system
User Context: The Work Process rolls the User related information into WP Task handlers. The User context is displayed in SU56.For Optimal performance, the User Authorizations should be as minimal as possible to reduce the Roll times.
Work Processes: These are used to Handle the user requests.These are displayed by using SAPMMC,SAPMC,dpmon,SM50 and SM66.
Task Handlers:
Each Work Process is having its own task handler which can be displayed by the using work process trace. These traces can be displayed using AL11,ST11,SM50(Process trace). These traces are stored in /usr/sap/SID/DVEBMGS00/work directory.
R3Buffer: it is used to store the most Frequently accessed and less freqeuntly modified/updated data. it is displayed in ST02. It Improves the Performance of the System by reducing the hits on the Database.
DB Client: it Provides set of executables to communicate with Database in the Native Language.it is provided by the database vendors(oracle corp,microsoft,ibm,sap).
SAP Kernel: it Provides set of executables/binaries/libraries to communicate with Hardware,Operating System, Database and in Native Language.These are specific to Unicode|Non_unicode,Operating System,32bit|64 bit Hardware and Database. These are provided by SAP.