After attending the CDC implementation session of CERN team in UKOUG 2009, new features of Oracle Streams technology introduced with 11g got my attention. While searching for a suitable resource, I came across with this extremely helpful resource.
The problem about many Oracle books is that they either paraphrase Tahiti (or Oracle My Support notes although it is illegal) or they are built on some pseudo examples generated just to create a problem to find a solution.This book is definitely an exception and it is not for my book-shelf but for my briefcase.
Thanks to Ann L. R. McKinnell and Eric Yen start with a few warm up chapter (Chapter 1) explaining the underlying concepts of streaming idea and its proper usage, Oracle CDC components, and a brief introduction to XStreams which will be detailed in Chapter 6.
Chapter 2 is for database architects who are responsible with designing the replication system such that it will work smoothly for their business. There is an invaluable check list including almost everything that should be taken into consideration before starting.
Chapter 3 is a kind of implementation chapter of Chapter 2. In order to satisfy the checklist given in previous chapter, this chapter defines the necessary configuration details.
Chapter 4, Chapter 5, and Chapter 6 explains different ways of replication in detail. Keep in mind that you can read Chapter 5 online.
Chapter 7 and Chapter 8 are my favorite ones and I believe those are the reasons why this book is an excellent reference for all implementors. Chapter 7 is explaining the importance of documentation in a replication environment and explain how you can automatically generate your environment map and how you can gather performance data with Oracle utility packages. Chapter 8 is all about troubleshooting in Oracle Streams environment. I think this is the most important part because people keep on changing what you have implemented. The methodology and toolkit to track,diagnose, and solve a problem in your streaming environment is put very clearly in two sub-chapters and 13 bulletins.
To sum up, Oracle 11g Streams Implementor’s Guide is a really niche reference for not only those try to implement an Oracle CDC environment but also wish to understand essence of replication concepts (almost all are the same with slight changes in terminology and the way they have been implemented).
In programming language theory, positional notation refers to matching the order of formal parameters and actual parameters. Whereas named notation refers to matching the formal parameters and actual parameters explicitly usually (not necessarily) by some operator (in PL/SQL this operator is =>). Finally mixed notation refers using both together as a single notation.
Although there was no restriction on using any of those notations within PL/SQL blocks, prior to 11g named & mixed notations for PL/SQL subroutines were not allowed in SQL statements (Code Piece 1 and Code Piece 2). This is one of the most restrictive issues about SQL for developers. Luckily 11g solves that issue and now it is allowed to use named and mixed notations also in SQL statements.
Yet Another Optimization or a Compiler Trick?
In Oracle 11g, Oracle finally allows PL/SQL developers to use sequences in PL/SQL expressions. Prior to that version developers should fetch the nextval or currval of a sequence by using a select … dual type of statements. By 11g you don’t need this anymore. You can simply refer to sequences anywhere you want within a PL/SQL expression.
In this paper you will find out basic usage example and whether this new syntax is a new PL/SQL optimization removing dual access necessity or it is only plastics.
Prior to 11g Oracle RMAN had a single compression algorithm, called BZIP2. The algorithm has a very satisfactory compression ratio in terms of decreasing the size of RMAN output. However, high CPU cost makes algorithm not suitable for many sites especially for sites having CPU bottleneck (Data warehouse DBAs?!?:)). As a result people still use hardware compression capabilities of tape drivers (ratios like 1:3) to decrease the backup time and increase the effective write speed of backup drivers. By 11g Oracle introduces a new compression algorithm that is announced to be less compressive but less aggressive in terms of CPU. In this paper you will find comparison of two algorithms with no compressed case.