create barcode labels c# Transactions and Concurrency in VB.NET

Generate Universal Product Code version A in VB.NET Transactions and Concurrency

10
Generating GS1 - 12 In Visual Basic .NET
Using Barcode creation for Visual Studio .NET Control to generate, create GS1 - 12 image in Visual Studio .NET applications.
www.OnBarcode.com
GS1 - 12 Scanner In VB.NET
Using Barcode decoder for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Transactions and Concurrency
Paint Bar Code In VB.NET
Using Barcode generation for .NET framework Control to generate, create bar code image in Visual Studio .NET applications.
www.OnBarcode.com
Scan Barcode In VB.NET
Using Barcode scanner for .NET framework Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Lock Escalation
Print UCC - 12 In C#
Using Barcode generation for .NET Control to generate, create UCC - 12 image in VS .NET applications.
www.OnBarcode.com
GTIN - 12 Printer In .NET Framework
Using Barcode creation for ASP.NET Control to generate, create UPC Symbol image in ASP.NET applications.
www.OnBarcode.com
SQL Server automatically escalates row, key, or page locks to coarser table or partition locks as appropriate. This escalation protects system resources it prevents the system from using too much memory for keeping track of locks and increases ef ciency. For example, after a query acquires many row locks, the lock level can be escalated because it probably makes more sense to acquire and hold a single lock than to hold many row locks. When lock escalation occurs, many locks on smaller units (rows or pages) are released and replaced by one lock on a larger unit. This escalation reduces locking overhead and keeps the system from running out of locks. Because a nite amount of memory is available for the lock structures, escalation is sometimes necessary to make sure the memory for locks stays within reasonable limits. The default in SQL Server is to escalate to table locks. However, SQL Server 2008 introduces the ability to escalate to a single partition using the ALTER TABLE statement. The LOCK_ESCALATION option of ALTER TABLE can specify that escalation is always to a table level, or that it can be to either a table or partition level. The LOCK_ESCALATION option can also be used to prevent escalation entirely. Here s an example of altering the TransactionHistory table (which you may have created if you ran the partitioning example in 7, Special Storage ), so that locks can be escalated to either the table or partition level:
Generate UPCA In .NET Framework
Using Barcode generation for Visual Studio .NET Control to generate, create UPC-A Supplement 5 image in .NET framework applications.
www.OnBarcode.com
Draw PDF 417 In VB.NET
Using Barcode maker for .NET Control to generate, create PDF-417 2d barcode image in .NET framework applications.
www.OnBarcode.com
ALTER TABLE TransactionHistory SET (LOCK_ESCALATION = AUTO);
Code39 Encoder In VB.NET
Using Barcode creator for Visual Studio .NET Control to generate, create Code-39 image in .NET applications.
www.OnBarcode.com
Bar Code Generation In VB.NET
Using Barcode drawer for Visual Studio .NET Control to generate, create bar code image in .NET applications.
www.OnBarcode.com
Lock escalation occurs in the following situations:
Generate EAN-13 In Visual Basic .NET
Using Barcode generator for VS .NET Control to generate, create GTIN - 13 image in Visual Studio .NET applications.
www.OnBarcode.com
EAN8 Maker In Visual Basic .NET
Using Barcode generator for Visual Studio .NET Control to generate, create GS1 - 8 image in .NET applications.
www.OnBarcode.com
The number of locks held by a single statement on one object, or on one partition of one object, exceeds a threshold. Currently that threshold is 5,000 locks, but it might change in future service packs. The lock escalation does not occur if the locks are spread over multiple objects in the same statement for example, 3,000 locks in one index and 3,000 in another. Memory taken by lock resources exceeds 40 percent of the non-AWE (32-bit) or regular (64-bit) enabled memory and the locks con guration option is set to 0. (In this case, the lock memory is allocated dynamically as needed, so the 40 percent value is not a constant.) If the locks option is set to a nonzero value, memory reserved for locks is statically allocated when SQL Server starts. Escalation occurs when SQL Server is using more than 40 percent of the reserved lock memory for lock resources.
Data Matrix Creator In C#.NET
Using Barcode encoder for VS .NET Control to generate, create Data Matrix image in VS .NET applications.
www.OnBarcode.com
PDF417 Maker In Visual C#
Using Barcode encoder for Visual Studio .NET Control to generate, create PDF417 image in VS .NET applications.
www.OnBarcode.com
When the lock escalation is triggered, the attempt might fail if there are con icting locks. So, for example, if an X lock on a RID needs to be escalated and there are concurrent X locks on the same table or partition held by a different process, the lock escalation attempt fails. However, SQL Server continues to attempt to escalate the lock every time the transaction acquires another 1,250 locks on the same object. If the lock escalation succeeds, SQL Server releases all the row and page locks on the index or the heap.
Generate Barcode In Visual C#.NET
Using Barcode encoder for Visual Studio .NET Control to generate, create barcode image in Visual Studio .NET applications.
www.OnBarcode.com
PDF-417 2d Barcode Scanner In Visual Basic .NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Microsoft SQL Server 2008 Internals
Create Quick Response Code In None
Using Barcode encoder for Word Control to generate, create QR Code image in Office Word applications.
www.OnBarcode.com
ECC200 Encoder In Objective-C
Using Barcode generation for iPhone Control to generate, create Data Matrix image in iPhone applications.
www.OnBarcode.com
Note SQL Server never escalates to page locks. The result of a lock escalation is always a table or partition. In addition, multiple partition locks are never escalated to a table lock.
Make Code 128A In Java
Using Barcode printer for BIRT reports Control to generate, create Code 128A image in BIRT applications.
www.OnBarcode.com
Paint Data Matrix ECC200 In Java
Using Barcode generator for BIRT reports Control to generate, create ECC200 image in Eclipse BIRT applications.
www.OnBarcode.com
Controlling Lock Escalation
Lock escalation can potentially lead to blocking of future concurrent access to the index or the heap by other transactions needing row or page locks on the object. SQL Server cannot de-escalate the lock when new requests are made. So lock escalation is not always a good idea for all applications. SQL Server 2008 also supports disabling lock escalation for a single table using the ALTER TABLE statement. Here is an example of disabling lock escalation on the TransactionHistory table:
ALTER TABLE TransactionHistory SET (LOCK_ESCALATION = DISABLE);
SQL Server 2008 also supports disabling lock escalation using trace ags. Note that these trace ags affect lock escalation on all tables in all databases in a SQL Server instance.
Trace ag 1211 completely disables lock escalation. It instructs SQL Server to ignore the memory acquired by the lock manager up to the maximum statically allocated lock memory (speci ed using the locks con guration option) or 60 percent of the non-AWE (32-bit) or regular (64-bit) dynamically allocated memory. At that time, an out-of-lock memory error is generated. You should exercise extreme caution when using this trace ag as a poorly designed application can exhaust the memory and seriously degrade the performance of your SQL Server instance. Trace ag 1224 also disables lock escalation based on the number of locks acquired, but it allows escalation based on memory consumption. It enables lock escalation when the lock manager acquires 40 percent of the statically allocated memory (as per the locks option) or 40 percent of the non-AWE (32-bit) or regular (64-bit) dynamically allocated memory. You should note that if SQL Server cannot allocate memory for locks due to memory use by other components, the lock escalation can be triggered earlier. As with trace ag 1211, SQL Server generates an out-of-memory error when memory allocated to the lock manager exceeds the total statically allocated memory or 60 percent of non-AWE (32-bit) or regular (64-bit) memory for dynamic allocation.
If both trace ags (1211 and 1224) are set at the same time, trace ag 1211 takes precedence. Remember that these trace ags affect the entire SQL Server instance. In many cases, it is desirable to control the escalation threshold at the object level, so you should consider using the ALTER TABLE command when possible.
Copyright © OnBarcode.com . All rights reserved.