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Caching and Transaction StateLocate this document in the navigation structure

Use

When the user navigates between Web pages, the Web browser retrieves an updated page from either the ICM or the Web browser cache. As a result, the Internet Transaction Server (ITS) is not always notified when the user navigates between pages.

Process

This behavior has consequences for programming Web transactions:

  • When you execute a transaction in the SAP GUI, pressing the Back (F3) button always sends an OK code back to the SAP system.

  • When you execute an SAP transaction from a Web browser, pressing the Back (F3) button does not always send a request back to the ICM (and subsequently to the SAP system), because the requested page may already reside in the Web browser cache.

    As a result, the SAP transaction is not notified and the current screen for the transaction may be out of phase with the one displayed in the browser.

Example

The following example illustrates the problem:

  1. Suppose the first transaction screen is a logon screen with number 1000. The corresponding HTML page will displays a logon screen in the user's Web browser.

  2. The user submits the logon data with a POST operation to the browser.

    The following page, an overview of the user's sales orders, is retrieved from SAP system, displayed, and put into the Web browser cache. The corresponding screen is number 2000.

  3. In the overview page, the user selects a sales order (with a hypertext link) to request detailed information.

    The detail page is retrieved from the Web browser using a GET operation. These pages are never cached. The corresponding SAP system screen number is 3000.

  4. In the detail page, the user navigates back to the overview page using the Web browser's Back button.

    Since the overview page was previously generated with a POST operation, it can be taken from the browser cache. As a result, no request is sent back to the SAP transaction. After using Back, the Web browser page corresponds to SAP transaction screen 2000, but the current screen in SAP system is still number 3000.

Since the Web browser displays the overview page, but the transaction still displays the detail screen (number 3000), the browser and transaction are out of sync. The result is that requests initiated from the HTML page are now processed by the wrong logic in the SAP system screen. Also, since the HTML page may contain input fields not present on the SAP system screen, user input can get lost.