The presentation did not make the cut of abstracts selected by Oracle. But if you want to see it at OOW, there’s still a chance! Just vote for the presentation on Oracle Mix (you’ll need to create an Oracle Mix account if you don’t already have one, but it’s free and a good way to meet people in the ADF community).
See you at ODTUG and/or OOW!
Continuing on from the last post, we’re looking at ways to tune ADF view objects for optimal performance and resource management.
In most applications, the user needs to be able to scroll through data both forwards and backwards–to return to a previous row in addition to simply being able to scroll forward, or to find rows an earlier view row after finding a later one. Because of this, by default, once rows from a view object’s query result are read into the view cache, they stay there. If your JDBC fetch size is 18, then initially, only 18 rows will be in the view cache, but when request rows outside the first 18, that number goes up to 36, then 54, then 72, and so on.
Now that we’ve looked at tuning entity objects and associations, we’ll turn to talking about tuning your ADF view objects for good performance and memory management. There’s a lot to say about tuning view objects (more than for any other business component, in my opinion), so I’m going to break this topic up over two posts. This week, we’ll discover the reasons for and against basing read-only view objects on entity objects, learn how to control how much data is fetched into the middle tier at one time (and how to optimize this for your particular case), and talk about what passivation of view objects is and how to control whether and how much of it happens. Next week, we’ll talk about query-level range paging, forward-only mode, and the spill-to-disk feature for handling very large caches.
Hey, did you know that, even if you create a “Programmatic View Object” (rows populated programmatically, not based on a query), you can set “bind variables” for it? Neither did I until very recently. You can’t do it in the Create View Object wizard (because the Query page never appears), but once you’ve got that VO, you can indeed add bind variables in the editor.
“Why on earth would you want to do that?” you ask (or, at least, I imagine you asking). “Bind variables are meant to allow the application or user to specify bind parameters for a query, and a programmatic VO doesn’t have a query.” Indeed, that’s what bind variables are usually for, but here, I’m going to show you, at least in outline, how to use this feature to make the ultimate 100% declaratively customizable framework classes (one view object class, one view definition class) for view object definitions based on REF cursors (i.e., whose instances will call a package function to retrieve their row set, rather than execute a query).