SQL performance can degrade for many reasons, some of most common are:
- plan changes
- data skewness
- low caching efficiency
- data growth
All these factors are relatively well known. A somewhat less common, although not exceptionally rare scenario, is read consistency overhead due to concurrent (more...)
Découvrez cette solution en suivant le webcast du 3 décembre : Database Cloning in Minutes using Enterprise Manager 12c Database as a (more...)
I heard a strange report from a client late last week - they weren't getting any smart scans on their Exadata - a data warehouse, no less (and we checked to see if cell_offload_processing was set to true). Queries would run normally, but for some reason, the "cell physical IO (more...)
Original Post can be viewed at 12c: Sqlplus Displays Last Login Time For Non – Sys Users
12c database has introduces a pretty nifty Security feature which allows you to check last login time for non-sys user. e.g If I connect to scott user as below, it displays that (more...)
I really didn't think we would be seeing 12c until OpenWorld. I got a nice surprise a couple of weeks ago when people started tweeting that the docs were out. That followed quickly with the actual software being available for download.
I realize that people won't really be producing (more...)
Original Post can be viewed at 12c:Limiting PGA with pga_aggregate_limit
This is a interesting feature for Oracle DBA’s. Till now there has been no way of limiting total PGA being used by oracle instance. _pga_max_size (hidden parameter) could be used to limit per process memory. SGA_TARGET used to be hard (more...)
how NOT to design (more...)
Oracle Database Gateways 11g R2 (11.2) Installation and Configuration for heterogeneous connection from Oracle to Microsoft SQL database
Install the Oracle Database Gateways 11g R2 (11.2). See the screen snapshots of the installation here.
- During the installation, the following default initialization parameter file is created:
dg4msql = Database gateway for Microsoft SQL Server. If you choose a different database option, (more...)
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 FROM dba_mview_analysis WHERE owner='JOHN'; MVIEW_NAME LAST_REFRESH_DATE FULLREFRESHTIM INCREFRESHTIM ------------------------ ---------------------- -------------- ------------- MV_CHANGE_HISTORY 07-JAN-13 04.36.58 PM 0 (more...)