Programming Guide



CONTINUE_DOWN

Fetches the next set of rows from the file

int sm_tm_command ("CONTINUE_DOWN [ tableViewName [ tableViewScope ] ]");

Arguments

tableViewName
The name of a table view in the current transaction. This parameter is case sensitive.

If tableViewName is specified, the command is applied according to the tableViewScope parameter. Since the entire table view tree might not be included, this is known as a partial command, and sm_tm_command sets TM_FULL to 0.

If tableViewName is not specified, the command is applied for each table/server view, starting with the root table view. This is known as a full command, and sm_tm_command sets TM_FULL to 1.

tableViewScope
One of the following parameters, which must be preceded by a table view name. TV_AND_BELOW which applies the command to the specified table view and all table views below it on the tree. If no parameter is specified, the transaction manager acts as though TV_AND_BELOW was supplied. BELOW_TV which applies the command to the table views below the specified table view. TV_ONLY which applies the command to the specified table view only. SV_ONLY which applies the command only to the table views of the specified server view.

Description

CONTINUE_DOWN (not available in Web applications or three-tier processing) fetches the next set of rows from the file. Note that even though the commands CONTINUE_DOWN and CONTINUE both display the next set of data, CONTINUE_DOWN generates different a request than CONTINUE.

The availability of CONTINUE_DOWN is dependent on the setting of the fetch_directions property for the server view or screen. If the fetch_directions property is set to PV_CONT_ALWAYS (Up/Down-all modes), this command is available in update or view mode. If the fetch_directions property is set to PV_CONT_VIEW_ONLY (Up/Down-view mode), this command is available only in view mode. Otherwise, an error is generated. For more information on setting the Fetch Directions property, refer to "Scrolling Through the Select Set" in Application Development Guide.

If your screen has multiple table views, the transaction manager issues a DBMS CONTINUE_DOWN for the specified table view and any table views linked to it via server links. This displays the next set of rows for that server view. Then SELECT or VIEW processing is done for any additional child table views.

The data displayed with this command is from a continuation file; it is not refetched from the database. Therefore, any updates made to the data in this server view either by you, or by another user, are not displayed. In order to display those updates, you must again fetch the data from the database with a VIEW or SELECT command.

The advantage of using Panther's continuation file is that it prevents having shared locks on data. However, if the fetch_directions property is set to PV_CONT_ALWAYS (Up/Down-all modes), you are responsible for implementing the necessary locking scheme for concurrent users. For more information on using the Version Column property to implement optimistic locking, refer to "Implementing Optimistic Locking" in Application Development Guide.

If you want to use the database engine's facilities for non-sequential scrolling, you need to add processing for the request events to the engine-specific transaction model.

Push buttons and menu selections for the CONTINUE_DOWN command can choose to set the class property to continue_button which activates the option only in view and update modes or to continue_view_button which activates the option only in view mode.

Sequence

Use CONTINUE_DOWN after SELECT or VIEW which generate a database query and display the first set of query results or after any other CONTINUE command.

Events

Table 8-9 Request event for CONTINUE_DOWN

Request Traversal Typical Processing

TM_CONTINUE_DOWN

The table views in the specified server view

See below

Table 8-10 Request and slice event processing for CONTINUE_DOWN

Slices Typical Processing

TM_CONTINUE_DOWN

A select cursor must have been set up for the server view encompassing the current table view or nothing more is done.

Calls sm_tm_continuation_availability to check if the command is available. If not, an error is issued.

On entry, TM_OCC_COUNT specifies the maximum number of occurrences to be fetched. If TM_OCC_COUNT is zero on entry, it means that there is no explicit limit being imposed. The TM_OCC member on entry specifies the first occurrence to be fetched into.

TM_OCC_COUNT is then zeroed. (At the end of this request, TM_SEL_CHECK sets it to contain the number of rows fetched.)

The data is fetched.

TM_SEL_CHECK is pushed onto the event stack to report the number of rows fetched.

TM_SEL_CHECK

If there was an error in earlier processing, give up the select cursor. Otherwise, report the number of rows fetched to TM_OCC_COUNT.

The following requests can be generated by the CONTINUE_DOWN command to ascertain if the changes from the previous command have been saved and, if desired, to discard those changes:

The following requests can also be generated for any child table views:

If TM_VIEW or TM_SELECT for a parent table view returns no data, TM_CLEAR requests are generated for all subordinate table views, but not for table views at the same level of the tree. TM_CLEAR requests are described under CLEAR.