HP Integrity NonStop J-Series - Manual (Page 101)

Figure 39 Parameters dialog
Enter a value, for example 1. The statement is executed, and the following tabs will appear in
Statement Details dialog:
•
Execution Results — Displays the output generated by the statement after the parameter is
replaced by the value you entered.
•
Execution Parameters — Lists p1 parameter with value 1.
•
Executed Statement — Contains Select t1 from T where t1 = 1 .
You can enter another statement that uses the parameter, p1. The statement will be executed. For
example, if you enter
Select * from T where T1 = $$p1$$ + $$p2$$ , the same dialog
appears. However, p1 (with value one) and p2 appear.
You can enter values again.
Page mode
When you execute a statement in the SQL Whiteboard, MXDM caches the results in virtual memory.
The SQL Whiteboard displays these results, but the virtual memory allotted for the SQL Whiteboard
can exhaust in the following scenarios:
•
A single query has a large result set consisting of a large number of columns or a large number
of rows, or both.
•
Several queries with large result sets are executed in a single SQL Whiteboard session.
To prevent an out-of-memory condition and accommodate large result sets, the SQL Whiteboard
can run in the page mode. In the page mode, the SQL Whiteboard breaks large result sets into
pages and retrieves one page at a time instead of retrieving all the data and displaying all rows
in the grid. The page mode reduces the memory usage because only a partial result is held in
memory and displayed in the Statement Details pane.
Default page mode operation
By default, the SQL Whiteboard displays all the results of a statement. However, it automatically
runs in page mode in the following scenarios:
•
Insufficient memory is available to display the result set in one page.
•
You specify a value from 1 to 100,000 in the Rows/Page field of the Statement pane. In this
case, if sufficient memory is available, the SQL Whiteboard automatically uses page mode
and allocates the number of rows per page that you specified.
Page mode considerations
The following considerations apply for page mode:
•
During the course of statement execution, MXDM frequently computes the available virtual
memory of the application. If the available virtual memory is less than an internal threshold,
statement execution happens in the page mode. You cannot modify this behavior. In some
cases, you must use the page mode to prevent MXDM from running out of memory and
generating an exception.
•
When a statement is executed and the number of rows is less than the Rows/Page threshold,
all rows in the results are retrieved and displayed in the grid.
Statement pane 101