When to consider sharding a MySQL database
Why should you not just design your applications from the start to account for data sharding? Sharding a database, that is horizontally partitioning tables among multiple databases, creates an added level of complexity that is not desirable in an application. However, there are times when sharding is required to maintain acceptable performance. So when is the right time to shard your database?
When to consider sharding a MySQL database Why should you not just design your applications from the start to account for data sharding? Sharding a database, that is horizontally partitioning tables among multiple databases, creates an added level of complexity that is not desirable in an application. However, there are times when sharding is […]
Schemas and users are frequently used interchangeably as if they were the same thing. For the most part, that's ok. In Oracle the concepts are so tightly coupled that thinking of them as the same thing is not really that far wrong.
In reality, a user is a database account that is given a password and permissions. A schema is a container, or namespace, for containing schema objects. Schema objects are things like tables, views and indexes.
In Oracle, when a us
The LAST_REFRESH_DATE column of the DBA_MVIEWS or the LAST_REFRESH column of the DBA_MVIEW_REFRESH_TIMES indicates the start refresh time. But what if we’d like to find out how long the refresh of the materialized view really takes. Well, we can query the DBA_MVIEW_ANALYSIS.
For Complete Refresh, the refresh duration will be in the FULLREFRESHTIM column of the DBA_MVIEW_ANALYSIS. For Fast Refresh duration, it will be in the INCREFRESHTIM column.
Both values are in seconds.
SELECT mview_name, last_refresh_date, fullrefreshtim, increfreshtim
MVIEW_NAME LAST_REFRESH_DATE FULLREFRESHTIM INCREFRESHTIM
------------------------ ---------------------- -------------- -------------
MV_CHANGE_HISTORY 07-JAN-13 04.36.58 PM 0 (more...)
An Oracle Database appliance is a set of standard hardware and software molded together to created a 2 node RAC cluster that is easy to deploy. In parts 1 & 2 i talked about what methods you can use to reformat or erase the Oracle Database Appliance and rebuild it. (more...)
There are occasions when you recieve a complete backup of a database from a place different then yours and have to do a restore. normally a restore is simple . put the files in a directory run rman catalog on them and you are done. but what if you have rman (more...)
InfoCaptor released the free online dashboard for every small business user in the entire universe.
The free dashboard is available at https://my.infocaptor.com and it is one of the most innovative dashboard in the Business Intelligence world.
With the online dashboard a small biz owner can automate its entire business reporting and set it on auto-pilot.
As a small business owner or a startup founder, there are gazillions of tasks that need to be performed on a day to day basis. If this is not enough the task list for a small operation keeps changing on a day to (more...)
Oracle Real Application Cluster (RAC) becomes the technology of choice for highly available and highly scalable deployment of enterprise Oracle database environment. With its innovative technology it comes with no surprise its complexity. The complexity is not only with the underlying database technology itself, but also how well you design and implement it to work with other components including operating system, storage subsystem, etc. In order to setup and maintain a successful RAC environment, it not only requires technical knowledge of database administrator (DBA), but also well collaboration and extended planning between all IT and business partners.
Few years (more...)
Recreate control file with the new DB name, the old tried and tested method.Method 2:
Use new utility called NIDSteps to rename Databases using the new NID utility:1.) Stop database
2.) startup mount the database:
[oracle@testing1]~% srvctl status database -d test
Instance test1 is running on node testing1
Instance test2 is running on node testing2
srvctl stop database -d test
[oracle@testing1]~% sqlplus / as sysdba
SQL*Plus: Release 184.108.40.206.0 Production on Thu Jul 21 00:50:44 2011
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Connected to an idle instance.
There was an interesting index related performance problem on Stack Overflow recently. The problem was to check an input string against a table that holds about 2000 prefix patterns (e.g.,
LIKE 'xyz%'). A fast select is needed that returns one row if any pattern matches the input string, or no row otherwise.
I believe my solution is worth a few extra words to explain it in more detail. Even though it’s a perfect fit for Use The Index, Luke it’s a little early to put it as an exercise there. It is, however, a very good complement (more...)
As of June 28, 2010 the Oracle APEX listener is available for download on the Oracle Technology Network (OTN) here
. The APEX listener in combination with a J2EE Web Server is a drop in replacement for Apache / ModPLSQL. Since Oracle Application Express (APEX) is deployed within an Oracle database (more...)
This article describes the effects of a high row migration rate on the clustering factor and the optimizer’s ability to select the best execution plan.
In my previous article—Row Migration and Row Movement—I have demonstrated that the “insert empty, update everything” anti-pattern can lead to 100% row migration. This article continues the research on row migration and unveils surprising effects on the clustering factor. To be precise, the clustering factor can become completely bogus in presence of a very high row migration rate. Once the clustering factor is “wrong”, it’s just a finger exercise to construct an optimizer (more...)