native barcode generator for crystal reports free download LOCKING AND LATCHING in Objective-C

Encoder Data Matrix in Objective-C LOCKING AND LATCHING

CHAPTER 6 LOCKING AND LATCHING
Data Matrix 2d Barcode Generation In Objective-C
Using Barcode encoder for iPhone Control to generate, create Data Matrix image in iPhone applications.
www.OnBarcode.com
Painting ANSI/AIM Code 128 In Objective-C
Using Barcode generation for iPhone Control to generate, create Code 128C image in iPhone applications.
www.OnBarcode.com
requestor to queue up and wait for the resource. With a latch request, the requestor session is told right away whether or not it got the latch. With an enqueue lock, the requestor session will be blocked until it can actually attain it.
Draw ECC200 In Objective-C
Using Barcode creation for iPhone Control to generate, create Data Matrix image in iPhone applications.
www.OnBarcode.com
Drawing GS1 128 In Objective-C
Using Barcode generation for iPhone Control to generate, create UCC.EAN - 128 image in iPhone applications.
www.OnBarcode.com
Note Using SELECT FOR UPDATE NOWAIT or WAIT [n], you can optionally decide not to wait for an enqueue lock
QR Code 2d Barcode Creator In Objective-C
Using Barcode encoder for iPhone Control to generate, create Denso QR Bar Code image in iPhone applications.
www.OnBarcode.com
Draw UPC - 13 In Objective-C
Using Barcode drawer for iPhone Control to generate, create UPC - 13 image in iPhone applications.
www.OnBarcode.com
if your session would be blocked, but if you do block and wait, you will wait in a queue.
Drawing Barcode In Objective-C
Using Barcode creator for iPhone Control to generate, create Barcode image in iPhone applications.
www.OnBarcode.com
Creating GS1 - 12 In Objective-C
Using Barcode printer for iPhone Control to generate, create UPC E image in iPhone applications.
www.OnBarcode.com
As such, an enqueue is not as fast as a latch can be, but it does provide functionality over and above what a latch can offer. Enqueues may be obtained at various levels, so you can have many share locks and locks with various degrees of shareability.
Encoding Data Matrix 2d Barcode In Visual C#
Using Barcode maker for VS .NET Control to generate, create Data Matrix image in Visual Studio .NET applications.
www.OnBarcode.com
Recognizing Data Matrix 2d Barcode In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
Latch Spinning
Generate UPC Symbol In .NET
Using Barcode drawer for VS .NET Control to generate, create UPC-A Supplement 2 image in .NET applications.
www.OnBarcode.com
Decoding Universal Product Code Version A In Visual Studio .NET
Using Barcode reader for .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
One thing I d like to drive home with regard to latches is this: latches are a type of lock, locks are serialization devices, and serialization devices inhibit scalability. If your goal is to construct an application that scales well in an Oracle environment, you must look for approaches and solutions that minimize the amount of latching you need to perform. Even seemingly simple activities, such as parsing a SQL statement, acquire and release hundreds or thousands of latches on the library cache and related structures in the shared pool. If we have a latch, then someone else might be waiting for it. When we go to get a latch, we may well have to wait for it ourselves. Waiting for a latch can be an expensive operation. If the latch is not available immediately and we are willing to wait for it, as we likely are most of the time, then on a multi-CPU machine our session will spin, trying over and over, in a loop, to get the latch. The reasoning behind this is that context switching (i.e., getting kicked off the CPU and having to get back on the CPU) is expensive. So, if the process cannot get a latch immediately, we ll stay on the CPU and try again immediately rather than just going to sleep, giving up the CPU, and trying later when we ll have to get scheduled back on the CPU. The hope is that the holder of the latch is busy processing on the other CPU (and since latches are designed to be held for very short periods of time, this is likely) and will give it up soon. If after spinning and constantly trying to get the latch, we still fail to obtain it, only then will our process sleep, or take itself off of the CPU, and let some other work take place. This sleep action is usually the result of many sessions concurrently requesting the same latch; it is not that a single session is holding it for a long time, but rather that so many sessions want it at the same time and each hold it for a short duration. If you do something short (fast) often enough, it adds up! The pseudo-code for a latch get might look like this: Loop for i in 1 .. 2000 loop try to get latch if got latch, return if i = 1 then misses=misses+1 end loop INCREMENT WAIT COUNT sleep Add WAIT TIME End loop;
Code 128 Reader In None
Using Barcode recognizer for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
Recognizing GS1 - 12 In Visual C#
Using Barcode reader for .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
CHAPTER 6 LOCKING AND LATCHING
Code 39 Extended Encoder In Visual Basic .NET
Using Barcode creator for Visual Studio .NET Control to generate, create Code 3 of 9 image in VS .NET applications.
www.OnBarcode.com
Paint Barcode In None
Using Barcode generator for Excel Control to generate, create Barcode image in Microsoft Excel applications.
www.OnBarcode.com
The logic is to try to get the latch and, failing that, to increment the miss count, a statistic we can see in a statspack report or by querying the V$LATCH view directly. Once the process misses, it will loop some number of times (an undocumented parameter controls the number of times and is typically set to 2,000), attempting to get the latch over and over. If one of these get attempts succeeds, then it returns and we continue processing. If they all fail, the process will go to sleep for a short duration of time, after incrementing the sleep count for that latch. Upon waking up, the process begins all over again. This implies that the cost of getting a latch is not just the test and set -type operation that takes place, but also a considerable amount of CPU while we try to get the latch. Our system will appear to be very busy (with much CPU being consumed), but not much work is getting done.
2D Barcode Printer In Visual Basic .NET
Using Barcode generator for .NET Control to generate, create Matrix Barcode image in .NET applications.
www.OnBarcode.com
Paint Code 128 Code Set C In C#.NET
Using Barcode creator for .NET Control to generate, create Code 128B image in .NET applications.
www.OnBarcode.com
Barcode Reader In Java
Using Barcode Control SDK for BIRT Control to generate, create, read, scan barcode image in BIRT reports applications.
www.OnBarcode.com
Print Barcode In Java
Using Barcode drawer for Android Control to generate, create Barcode image in Android applications.
www.OnBarcode.com
Copyright © OnBarcode.com . All rights reserved.