First Checkbox in header - selects all available records or only showing records (excluding pagination)

Question

While showing hundreds of records in a table, I am dividing it in set of 10 records. First column is for check boxes for selecting record(s). User can select one or multiple records and clicks the primary action button which is below this table.

Now if user selects the topmost check box which is in the header row,

Does it mean user has selected all the records available (irrespective of pagination) OR Does it mean only first 10 records are selected and will be acted upon?

Is there any study/research available to support the answer?

In second case, only 10 records are selected on click of the header check box, how can I show a check box which actually selects all available records (and after clicking primary button, action is performed! This is a must requirement).

[Placing a new primary action button besides existing action button; lets say 'ACT for ALL' (for selecting all records and acting on those) might not work here because sometimes user does select all the records and then unchecks a few, and then presses primary action button]

I don't want to use first check box in header acts like selecting all available records because this feature is of selecting all available records and acting on those is for few table sets/task flows and not for all. Using it globally for select all will confuse user as there wont be any consistency.

Answer 1

Convention dictates that when selecting a top checkbox you select the items that are showing in the current page, ie. not the items on additional pages.

This is the behaviour of both Google and Hotmail in their mail inbox.

Note however that this can be combined, as Google has it, with additional controls to enable selection of all items in the table, which enhances user control.