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Oracle Flashback options

A brief history about Oracle Flashback , its starting version, various enhancements, What it uses to manage the flashback.

Version Flashback Option available Provides Uses Depends on 9i Flashback Query allows the user to query the data at some point-in-time in the past to reconstruct the lost data that may have been deleted or changed […]

Quiz Post #12: when does your session/sid/statement appears in V$session_longops

We all know that when a query/statement is running from long time (actually this post is meant to know at what times :)) , the access path will be shown in v$session_longops

Some of the access paths are as below

Table scan; Index Fast Full Scan; Hash join; Sort/Merge; Sort Output; Rollback; Gather Table’s Index […]

Quiz Post# 11: How many GES resources for a RAC instance?

How to measure the GES Resources (enqueues for RAC ) limit in RAC?

Oracle preserves the integrity of the users data during simultaneous use of the same data blocks by different instances using GCS. In addition to data blocks, many other shared resources can be concurrently accessed by end users. Oracle uses a queuing mechanism […]

Oracle RAC Wait events

RAC Wait Event Naming Conventions

Events that start with “GCS%” and “gc%” are Cache Fusion-related waits. In other word, they have to do with waits experienced in shipping current or consistent-read versions of blocks across instances in a RAC cluster

Events that start with “ges%’ are related to Global Enqueue Services

Block-Oriented RAC Waits


RAC Wait Events: Where is “gc buffer busy”? gc buffer busy acquire vs. gc buffer busy release.

I raised a SR that am not able to see the gc buffer busy wait event as expected and eventually got to know that it is no more.

Before proceeding, what is gc buffer busy? Event ‘gc buffer busy’ event means that a session is trying to access a buffer,but there is an open request […]

Quiz Post #10: What are the meanings for different letter for awr base tables WR#

Oracle 10g provides the Automatic Worload Repository. The AWR is a repository of performance information collected by the database to aid in the tuning process for DBAs. The main focus for the Oracle database in version 10g is self-manageability. AWR is  the place where the data to aid in self-management is stored.


Clone Database: Turn your backup (rman image copy) to a database without copy/restore?

Imagine how it could be if you can use your image copies of your databases as your UAT/dev databases, without much usign complex restore procedure, how it could be if you refresh/clone the databases.

The answer is is using Oracle Direct NFS Client and dbms_dnfs package.

Clonedb is a new Direct NFS (DNFS) feature introduced […]

Data Pump: Expdp/impdp legacy support.


Am trying to use expdp, Watch this screenshot closely

and you ever wonder that how does it works, as I have used , row=n, file=test1.dmp with expdp which should not work but it is.


11g RAC Failover Test Cases

Hello All,

We all build RAC infrastructure and we have seen many cases that environment is not stable after live or when start using it.

The reasons may be many, but due to vast technologies involvement in high availability concepts we do not know or we ignore many aspects while doing environment testing.

It is […]

ORA-02082: a loopback database link must have a connection qualifier

One more for today,

Here is the error, this database link should point to production db,

SQL> create database link PRODDB connect to admin identified by admin using ‘PROD’; create database link MQDB connect to strmadmin identified by strmadmin using ‘PROD’ * ERROR at line 1: ORA-02082: a loopback database link must have a connection […]