ICM (SMICM) and Gateway (SMGW) Differences and comparison:
ICM and gateway are two ends of SAP systems communications. Through gateway system communicates with other SAP and Non SAP system e.g. SAP:BW,CRM,SCM: Non SAP : vertex,taxware so on .ICM helps to make communication with internet .So if there is any error in HTTP ,HTTPS and SMTP(Mail ) we always check logs in SMICM.
Always differentiate any issue in two parts when there is communication with user and other systems :
1- When other systems are not able communicate with your sap system always make sure responsible RFC’s are working fine. Then check Gateway logs .Gateway logs always check with SMGW tcode. Details about logs and SMGW administration will discussion detail
2- When there is some issue reported by end users regarding connection issue with SMTP ,HTTP and HTTPS .We always check SMICM(ICM) logs to verify what is the error and how could be verified .
Let’s have some light how SMICM works and what are different influencing factor for the same:
*** Why I have make comparison between SMICM And SMGW because both are communication point to other system and user. Both are playing very important role for SAP motive of system integration .If SMICM not working your end user can’t work and whenSMGW not working No data can flow from to system . *****
SMICM: Is the transaction which monitor and administer Internet Communication Manager, Which sends and receive requests to and from the internet.ICM must be up and running to access SMICM .
ICM Monitor:
SMICM provides various functions to monitor ICM and identify if there is any error in logs:
Most of the monitor related functions are available in GOTO menu options .Following is the list of some useful functions :
Trace Files
To display or reset the trace file dev_icm, choose Go To ® Trace File or Go To ® Trace Level. You can also set the trace level here (values can be between 0 and 3; the default is 1). You can also display just the start or the end of the file (the first or last 1000 lines). This is a very useful function for large files. Choose Goto ® Trace File ® Display Start or Display End.
Dev_icm : this is the trace file of ICM available at /usr/sap/SID/<Central instance>/work.
Parameters
Choose Goto ® Parameters to display or change the ICM profile parameters. If you choose Change, you can display the RZ11 documentation for every parameter that is executed by placing the cursor on the parameter name and choosing
Note : Dynamic parameters are effective immediately but revert to parameter value once restart
Statistics
Choose Goto ® Statistics to activate, deactivate, display, and reset the ICM statictics.
Memory Pipes
Choose GoTo ® Memory Pipes for information on the memory pipes that are used for data exchange between the ICM and the work process.
What are memory Pipes: ICM communicates with Java engine using HTTP and ABAP engine using Memory pipes
Host Name Buffer
The mapping of host names to IP addresses or of service names to port numbers is buffered in the SAP System, once they have been read from the file system.
If a host name or a service name that should be accessed is changed, the host name buffer must be reset. You can display the buffer contents and reset the buffer. Then the ICM reads the updated data from the file system.
To do this choose Goto ® Host Name Buffer ® Display or Reset.
Services
Choose Goto ® Services to monitor and administer the services (ports that are used for the ICM connections
Release Information
Choose Goto ® Release Info or choose Release Info to display information about the version of the ICM, the release and the patch level of the SAP kernel.
The first line contains general information on the ICM.
You can see the status of the SAP kernel from kernel information. As well as the kernel release and compile information, you can find the following numbers.
· update level specifies the kernel status with which the kernel can run in an SAP system. If different application servers should run in a system with different kernel patch statuses, they must all have the same update level.
· patch number specifies the last patch level that is relevant for the component ICM.
· source id (the numbers after the point) indicates the actual kernel patch level.
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HTTP Server Cache
Here you can find functions for Monitoring and Administrating the ICM Server Cache.
HTTP Log
Choose Goto ® HTTP Log you can display the following information about logging HTTP requests. The functions are available for HTTP logging for servers as well as for clients.
· Display entries: Display the entries in the logging file
· Information: Name of the log file, format of the log file, terms for new log files, maximum log file size, cyclical write (yes/no), current number of characters in the log file and the current number of lines in the file.
· Write buffer: The logging file entries are buffered and are regularly written to the hard disk. Since you can only see the entries that are already on the hard disk with Display Entries, you can use this function to force the buffer contents to be written to the hard disk.
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HTTP Server
By choosing Goto ® HTTP Server you can display information on the HTTP application server
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If no J2EE Engine has been configured,
J2EE Server configured = FALSE, then
all HTTP requests are passed to the ABAP Engine .
If a J2EE server is connected, the ICM decides, using the URL prefix table, whether the request is sent to the ABAP or the J2EE Engine. All URL prefixes in the table are sent to the ABAP Engine, all others are sent to the J2EE Engine.
If no J2EE Engine has been configured, the table is not loaded.
You can however enforce this using Load URL Prefixes
*** Other part of SMICM is also available in like J2ee administration and HTTP server cache administration .But now we are just doing the small comparison between SMICM and SMGW then We will look into detail in further topics ***
What would happen if your Gateway is not working?
1- No RFC is working
2- No connection with other sap system and non sap systems
3- In dual stack case : No connection between ABAP instance and JAVA instance. Java instance will go down. But as per new scenarios Netweaver 7.10 Onwards JAVA instance and ABAP instance would be working independently and communicate through JCO rfc connection only. So there is no master slave concept between java instance and ABAP instance (My concept) .Why I have called ABAP as master instance and Java as slave .Because ABAP start java instance and Java instance can be stopped independently. Without affect ABAP instance .But You can to run java instance without ABAP instance.
ARCHITECTURE OF THE SAP GATEWAY
Each instance of an SAP System has a gateway. The gateway enables communication between work processes and external programs, as well as communication between work processes from different instances or SAP Systems.
Gateway Processes
The SAP Gateway is made up of various processes:
· Gateway read process
· Gateway monitor
These processes are described in the following topics.
Note :Earlier gateway releases that support DCAM and SNA have additional gateway work processes(gwwp, gwwp.exe).
Gateway Read Process
Gateway read (gwrd, gwrd.exe) is the main process in the gateway system.
It is started by the application server (dispatcher) and checked by it periodically.
The gateway reader receives and processes all CPI-C requests.
Note:
If the executable gwrd program is called without parameters or with the switch -help, the program outputs a description of the possible command parameters, as well as all the patches
Gateway Monitor
The gateway monitor (gwmon, gwmon.exe) is used to analyze and administer the SAP Gateway.
When you start it, you initially get a list of active CPI-C connections. You can call up all the other monitor functions via a menu.
You can monitor the gateway from the SAP System (transaction SMGW) or from the operating system.
SMGW:
DISPLAYING CLIENTS CURRENTLY LOGGED ON
You can display a list of currently logged on systems via Goto ® Logged on systems .
The following values are displayed for each system that is logged on:
· LU Name: With CPIC connections via TCP/IP, this field describes the host on which the partner program is running or supposed to run.
Note:
The term "logical unit" is a term borrowed from SNA and describes a logical node in an SNA network. The remote partner program is intended to run on this node.
· TP Name: Name of the transaction program or the name of the program that was started by the gateway.
· System Type The following values are possible:
· ¡ NORMAL_CLIENT : Normal client (external program)
· ¡ LOCAL_R3: Local SAP System
· ¡ REMOTE_GATEWAY: connection to remote gateway
· ¡ FROM_REMOTE_GATEWAY: connection from a remote gateway
· ¡ REGISTER_TP: Registered transaction program
· Host Name: Name of host client is running on
· Host Address: All TCP/IP names on the host. If there are several network cards then there may be several entries here. Usually 5 alternative host names are supported.
· Last Req: Time of last activity
· Status: Connection status to a client or another gateway at TCP/IP level. The default value is CONNECTED.
In the following cases connections are highlighted in color in the gateway monitor.
· ¡ Connections with status PENDING (handshake while opening the connection) are colored orange
· ¡ If the data packets could not be fully written in the network connections, the connection is colored green. If this status lasts for a while, it indicates network problems, or the partner program cannot read any data from the network, because it is busy with other tasks that take time (for example, BRBACKUP).
By choosing Goto ® Logged On Systems, you can either delete a client or display detailed information.
1 comment:
Thank you very informative.
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