native barcode generator for crystal reports crack High-water Mark in Objective-C

Creation Data Matrix in Objective-C High-water Mark

High-water Mark
DataMatrix Encoder In Objective-C
Using Barcode generation for iPhone Control to generate, create DataMatrix image in iPhone applications.
www.OnBarcode.com
Code 3 Of 9 Printer In Objective-C
Using Barcode creation for iPhone Control to generate, create ANSI/AIM Code 39 image in iPhone applications.
www.OnBarcode.com
This is a term used with table segments stored in the database. If you envision a table, for example, as a flat structure or as a series of blocks laid one after the other in a line from left to right, the high-water mark (HWM) would be the rightmost block that ever contained data, as illustrated in Figure 10-1.
Drawing Universal Product Code Version A In Objective-C
Using Barcode encoder for iPhone Control to generate, create Universal Product Code version A image in iPhone applications.
www.OnBarcode.com
Paint ECC200 In Objective-C
Using Barcode generator for iPhone Control to generate, create DataMatrix image in iPhone applications.
www.OnBarcode.com
CHAPTER 10 DATABASE TABLES
Barcode Printer In Objective-C
Using Barcode maker for iPhone Control to generate, create Barcode image in iPhone applications.
www.OnBarcode.com
Draw EAN-13 In Objective-C
Using Barcode drawer for iPhone Control to generate, create EAN / UCC - 13 image in iPhone applications.
www.OnBarcode.com
Figure 10-1. Depiction of an HWM Figure 10-1 shows that the HWM starts at the first block of a newly created table. As data is placed into the table over time and more blocks get used, the HWM rises. If we delete some (or even all) of the rows in the table, we might have many blocks that no longer contain data, but they are still under the HWM, and they will remain under the HWM until the object is rebuilt, truncated, or shrunk (shrinking of a segment is a new Oracle 10g feature that is supported only if the segment is in an ASSM tablespace). The HWM is relevant since Oracle will scan all blocks under the HWM, even when they contain no data, during a full scan. This will impact the performance of a full scan especially if most of the blocks under the HWM are empty. To see this, just create a table with 1,000,000 rows (or create any table with a large number of rows), and then execute a SELECT COUNT(*) from this table. Now, DELETE every row in it and you will find that the SELECT COUNT(*) takes just as long (or longer, if you need to clean out the block! Refer to the Block Cleanout section of 9 Redo and Undo to count 0 rows as it did to count 1,000,000. This is because Oracle is busy reading all of the blocks below the HWM to see if they contain data. You should compare this to what happens if you used TRUNCATE on the table instead of deleting each individual row. TRUNCATE will reset the HWM of a table back to zero and will truncate the associated indexes on the table as well. If you plan on deleting every row in a table, TRUNCATE if it can be used would be the method of choice for this reason. In an MSSM tablespace, segments have a definite HWM. In an ASSM tablespace, however, there is an HWM and a low HWM. In MSSM, when the HWM is advanced (e.g., as rows are inserted), all of the blocks are formatted and valid, and Oracle can read them safely. With ASSM, however, when the HWM is advanced Oracle doesn t format all of the blocks immediately they are only formatted and made safe to read upon their first actual use. The first actual use will be when the database decides to insert a record into a given block. Under ASSM, the data is inserted in any of the blocks between the low high water mark and the high water mark, so many of the blocks in this area might not be formatted. So, when full scanning a segment, we have to know if the blocks to be read are safe or unformatted (meaning they contain nothing of interest and we do not process them). To make it so that not every block in the table needs go through this safe/not safe check, Oracle maintains a low HWM and a HWM. Oracle will full scan the table up to the HWM and for all of the blocks below the low HWM, it will just read and process
Paint QR Code In Objective-C
Using Barcode creator for iPhone Control to generate, create QR Code 2d barcode image in iPhone applications.
www.OnBarcode.com
UPC - 8 Maker In Objective-C
Using Barcode encoder for iPhone Control to generate, create EAN / UCC - 8 image in iPhone applications.
www.OnBarcode.com
CHAPTER 10 DATABASE TABLES
Printing ECC200 In C#.NET
Using Barcode encoder for Visual Studio .NET Control to generate, create Data Matrix ECC200 image in Visual Studio .NET applications.
www.OnBarcode.com
Data Matrix ECC200 Recognizer In None
Using Barcode decoder for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
them. For blocks between the low HWM and the HWM (see Figure 10-2), it must be more careful and refer to the ASSM bitmap information used to manage these blocks in order to see which of them it should read and which it should just ignore.
Data Matrix Generation In None
Using Barcode generation for Software Control to generate, create ECC200 image in Software applications.
www.OnBarcode.com
Drawing QR Code 2d Barcode In Java
Using Barcode creation for Java Control to generate, create QR Code ISO/IEC18004 image in Java applications.
www.OnBarcode.com
Create Barcode In .NET
Using Barcode encoder for Visual Studio .NET Control to generate, create Barcode image in .NET applications.
www.OnBarcode.com
QR Code Drawer In None
Using Barcode generation for Software Control to generate, create QR Code JIS X 0510 image in Software applications.
www.OnBarcode.com
ECC200 Maker In Visual Basic .NET
Using Barcode drawer for VS .NET Control to generate, create Data Matrix image in VS .NET applications.
www.OnBarcode.com
QR Code ISO/IEC18004 Printer In Java
Using Barcode printer for Java Control to generate, create Denso QR Bar Code image in Java applications.
www.OnBarcode.com
Barcode Decoder In C#
Using Barcode Control SDK for VS .NET Control to generate, create, read, scan barcode image in VS .NET applications.
www.OnBarcode.com
Data Matrix Recognizer In None
Using Barcode decoder for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
Barcode Generator In Java
Using Barcode creator for Java Control to generate, create Barcode image in Java applications.
www.OnBarcode.com
Barcode Scanner In Visual C#.NET
Using Barcode scanner for .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Copyright © OnBarcode.com . All rights reserved.