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New ArticlesWelcome
Flashback Snapshot of Schema...(2014-02-19) [Doc]
Consistent Gets may not tell the truth...(2013-10-24) [Doc]
Oracle 12c Hybrid Histogram...(2013-08-27) [Doc]
Oracle 12c TOP-N Frequency Histogram...(2013-08-21) [Doc]
Rescue data in the worst situation (2)...(2013-03-20) [Doc]
Rescue data in the worst situation (1)...(2013-03-19) [Doc]
Understand Buffer Cache in further --- Build up queryable Buffer Cache Chain data...(2013-02-06) [Doc]
Oracle SQL Hints --- Contents...(2013-01-16) [Doc]
Oracle SQL Hints --- Other Hints...(2013-01-08) [Doc]
Oracle SQL Hints --- Model Query And Partition Hints...(2013-01-08) [Doc]
Hello DBA

Welcome to Fuyuncat(Wei Huang)'s personal web site. Built in 2005.
 Flashback Snapshot of Schema

 by fuyuncat

A way to create flashback snapshot for a schema in Oracle.

 Consistent Gets may not tell the truth

 by fuyuncat

Consistent gets is important statistics data indicating the performance of a SQL. It's a metric data for us to tune SQL. Normally, we may compare the performance of two SQL or same SQL with different execution plan. However, sometimes, CG may not tell us the release performance of SQL. Let's review below 2 statistics data output first.

 Oracle 12c Hybrid Histogram

 by fuyuncat

In 12c, a new feature of the optimizer is that it provides new type histogram statistics data for the columns, TOP-N frequency histogram and HYBRID histogram. With them, the optimizer can choose a best execution plan more efficiently and accurately. Here I will talk about the Hybrid Histogram, how the statistics gather process generate it, and how it impact the optimizer to calculate the selectivity.

 One single SQL helps you to analyze the performance of a SQL

 by fuyuncat

This is the script I am using to analyze SQL performance. It major contains one SQL only. It can show most of detail information about the SQL if available. And you can shoose to show parts of them.

 Fy_Recover_Data 2014.03.07 Update -- You can recover truncated table from offline data files now

 by fuyuncat

In case you found that you truncated a table should not be done. You may copy the data files of the tablespace to a local location. And then use Fy_Recover_Data to recover data from those offline files. This will guarantee minimuming data lost.

 Fy_Recover_Data Update (2014-02-20) --- Support ASM now!

 by fuyuncat

Fy_Recover_Data can recover the truncated table created on ASM now.

Products Update Welcome
One single SQL helps you to analyze the performance of a SQL...(2014-03-12) [Prod]
Fy_Recover_Data 2014.03.07 Update -- You can recover truncated table from offline data files now...(2014-03-07) [Prod]
Fy_Recover_Data Update (2014-02-20) --- Support ASM now!...(2014-02-19) [Prod]
Erratum of "Oracle SQL Optimizing and Tuning Technologies"...(2013-01-11) [Prod]
Oracle SQL Hints...(2013-01-08) [Prod]
Scripts of "Oracle SQL Optimizing and Tuning Technologies"...(2013-01-07) [Prod]
Fy_Recover_Data --- A PLSQL package to recover (Truncated) data...(2012-08-14) [Prod]
OraTracer Upgrade...(2012-06-29) [Prod]
FyDB becomes an open source project...(2011-08-09) [Prod]
FyDB --- a distributed in-memory NOSQL DB...(2011-07-07) [Prod]
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