Error Handling Using the ICM 

If the ICM determines an error, in most cases it returns a static text to the browser:

 

If this error page is too detailed for you due to security reasons, you can set parameter is/HTTP/show_detailed_errors to FALSE. The details will then be suppressed and the page will look like:

You can also configure the ICM (and the SAP Web Dispatcher) so that it returns dynamic error pages. The following section describes how you do this.

The ICM recognizes the following errors.

Error Name	Meaning
ENOMEM	The SAP Web AS is out of memory to process the request
ETIMEOUT	The SAP Web AS did not return a response within a specified period of time
ENOTAVAIL	A service is temporarily not available (for example, due to system overload or maintenance).
ENOTFOUND	The resource specified in the URL does not exist or it cannot be found (for example, a file in the file system)
ENOSESSION	The session for the session cookie no longer exists
ENOSSLREQ	SSL is expected on this port, no plaintext
EOVERLOAD	The SAP Web AS is overloaded and cannot accept any more requests
EPERM	Access is refused (for example, at the SAP Web dispatcher)
EPROTERROR	HTTP protocol error (incorrect syntax, missing header fields,...)
EMAINTENANCE	ICM / Web Dispatcher is in the Maintenance Mode.
EINTERN	ICM internal error (unspecific)

For each of these errors, an HTML page can be created which is sent to the client when the error occurs. You can define both static pages (ending .html) and dynamic pages (ending .shtml).

Moreover, you can create a file ICMERR-EDEFAULT.{html,shtml} in directory icm/HTTP/error_templ_path, whose contents are returned if there is no other template for the error.

If external resources (such as images) should be referenced in the error templates, these can be delivered with the ICM’s file access handler. See also icm/HTTP/file_access_<xx>.

Prerequisite for Using Your Own Error Pages

To use the ICM’s dynamic error handling, you must set the profile parameter icm/HTTP/error_templ_path to the directory with the error template files. For example:

icm/HTTP/error_templ_path = /usr/sap/B6M/D13/data/icmerror

Static Error Pages

If a static error page is defined for an error (ending .html), this is returned to the client.

Dynamic Error Pages

The dynamic pages support the following SSI commands (server-die includes, see http://hoohoo.ncsa.uiuc.edu/docs/tutorials/includes.html).

For the dynamic substitutions, the whole file must be searched for the SSI tags "<!--". The effort required to do this is related to the size of the file. The dynamic pages cannot be stored in the cache either.

The following section explains the SSI commands that are supported.

ECHO

 <!--#echo var="variable" -->

You can set the following variables:

Variable Name	Meaning
DATE_LOCAL	Current time/date: Tue Mar 26 17:15:32 2002
DATE_GMT	Current GMT time/date: Tue Mar 26 17:15:32 2002
LAST_MODIFIED	The time when the current file was last modified
FILE_SIZE	Size of the current file in Bytes
SERVER_SOFTWARE	SAP Web Application Server 6.30
SERVER_NAME	The name of the server
SERVER_PORT	The server port
PATH_TRANSLATED	URL path (without parameters)
ICM_SERVER	Host name and port through which this server can be reached. For example: Is3022.wdf.sap-ag.de:1080
ICM_INSTANCE	Instance name: ls3022_BIN_12
ICM_ERR_CODE	Error that occurred (numeric)
ICM_ERR_VERSION	ICM version
ICM_ERR_COMPONENT	Component
ICM_ERR_MODULE	Module name
ICM_ERR_LINE	Line
ICM_ERR_DETAIL	Detail on the error that occurred

Not all fields are available for all errors.

With error ICMEOVERLOAD, for example, the request has not yet been read, which is why field PATH_TRANSLATED has not been set.

In your page you can write, for example:

<tr><td>Server:</td><td><!--#echo var="ICM_SERVER" ‑‑></td></tr>

</tr><tr><td background="http://<!--#echo var="ICM_SERVER" ‑‑>/images/graybar_tile.jpg" height="31">

INCLUDE

You can use this command to include a different file at this point.

<!--#include file="file name" -->

Your error page can be framed, for example, by the two INCLUDE statements:

<!--#include file="header.html" -->

...

<!--#include file="footer.html" -->

The file must not include itself! Recursive inclusion causes the ICM to terminate.

You can find an example of a dynamic error page and the .shtml file in Examples of a Dynamic Error Page.

Prioritizing Using the ICM

If parameter icm/HTTP/error_templ_path is not set, the ICM static error page is always returned.

If parameter is set, when error <ERRNAME> occurs, the ICM first checks whether file ICMERR‑<ERRNAME>.html is located in the directory specified by icm/HTTP/error_templ_path, and sends it to the client. If it cannot find this file, it searches for ICMERR<ERRNAME>.shtml and returns it.

In no specific error page can be found, the ICM returns the default error page ICMERR-EDEFAULT.{html,shtml}(see above). If this file also does not exist, the static page is returned.

Updating Error Pages

For reasons of performance, the ICM checks once the error templates that are available. This is why you must restart the ICM if you add new templates (changes to the templates are recognized). You can use the ICM Monitor to restart it (Transaction SMICM) (see Monitoring the ICM Using the ICM Monitor).