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z/OS Block Mode Screen Design › Scrolling List › Scrolling Modes › Scroll Amounts

Scroll Amounts

The scroll amount determines how many lines of data are scrolled forward or backward in the viewport. There are six scroll amounts.

The following table shows scroll amount and viewport displacement.

Scroll Amount

Description

PAGE

Data scrolls forward or backward based on the total number of lines in the viewport. The viewport displacement is the size of the viewport. When the command is NEXT, the displacement is added to the current viewport origin. When the command is PREV, the displacement is subtracted from the current viewport origin.

HALF

Data scrolls forward or backward based on half of the number of lines in the viewport. The viewport displacement is half the size of the viewport rounded down an integer. The displacement must be at least one. When the command is NEXT, the displacement is added to the current viewport origin. When the command is PREV, the displacement is subtracted from the current viewport origin.

CURSOR

Data is displayed in the viewport so that the row that contains the cursor is either the first row or last row in the viewport. The displacement is the same as it is for PAGE when the cursor is on the:

First row of the viewport and NEXT is selected.

Last row and PREV is selected.

MAX

The viewport origin is relocated to either the first row or the last row of the data view.

When the command is PREV, the viewport origin is located to the first row.

When the command is NEXT, the viewport origin is located to the last row. If the view is protected, the last row is the last populated row. If the view is not protected, the last row is the last row in the data view extent. This row may or may not be populated.

LOCATE

The viewport origin is relocated to the line number entered by the user. The line number cannot be zero or a negative number. If the number is larger than the number of rows in the data view extent, then the viewport is relocated to the last row of the data view, just as it would be for a MAX NEXT command.

NUMERIC

The viewport origin is relocated based on a number entered by the user. The number is the viewport displacement that is added to, or subtracted from, the viewport origin. The number cannot be zero or a negative number. This is similar to PAGE scrolling, except that the displacement equals a number provided by the user instead of the number of rows in a viewport.

The Page, Half, Cursor, and Numeric displacement scroll amounts are retained after they are set. The Locate and Max scroll amounts are processed and then discarded, returning the scroll amount to its previous setting. The setting remains in effect until the user changes the scroll amount to a different value.

Also, Page is the scroll amount assigned when an application is started without a profile, or reset if a profile exists. If a restart is performed and a valid profile exists, then the scroll amount is recovered from the profile and reset to the last value it had in the application.

Processing of all scroll actions is performed using a two-phase process which depends on the following criteria:

In the first phase, the viewport origin is relocated based on the scroll request. In the second phase, the viewport origin is evaluated, a post processing action is performed, and the viewport origin is relocated if needed. The second phase processing depends on the mode of scrolling used, and the protection property of the repeating group view being scrolled.