Category Archives: Oracle

SQL query to check table size in Oracle database

In order to check size of table in Oracle database you may use following query:



How to: check currently used credentials for database connection in Oracle SQL Developer 4

When you are using Oracle SQL Developer 4 to connect to multiple databases at the same time (sometimes using credentials other than saved in connection properties) you have multiple tabs in main window labeled with DB names without any indication of under which account you are connected to them (it seems natural to have such information in tab label/name).

So your options here is either create multiple saved connections for each credentials used and name connections so that they reflect both DB name and credentials (after that using drop box in top right corner of main window comes in really handy) or use a query to check which credentials are currently being used.

You may use following query to check your currently used credentials:

\n[code language=”sql”]\nSELECT username,\nosuser,\nmachine,\nschemaname\nFROM gv$session\nWHERE sid=(SELECT sys_context(‘userenv’,’sid’) FROM dual);\n[/code]\nThis will give you USERNAME, OSUSER and MACHINE info. Or, alternatively you may use this (less details, but also less privileges required)​:\n[code language=”sql”]\nSELECT USER,SYS_CONTEXT (‘USERENV’,’SESSION_USER’) FROM dual\n[/code]\nThis returns USER and SYS_CONTEXT.


Review: Oracle 12c For Dummies (For Dummies

Oracle 12c For Dummies (For DummiesOracle 12c For Dummies (For Dummies by Chris Ruel\nMy rating: 4 of 5 stars

For Dummies series does amazing job in explaining everything in plain language without dramatic loss of depth or excessive oversimplification. They are very good to get you started with the subject.\nMy first tech book long time ago was Networking for Dummies (in Russian), and it was both fun to read and informative, all my tech knowledge prior that was based upon trial and error approach 🙂 Probably should re-read latest edition of Networking for Dummies for the sake of knowledge refresh and very good memories of 1st experience of for Dummies series :)\nAs for Oracle 12c book: I preordered digital edition from Amazon, and overall it nicely covers quite a wide array of things you need to know to approach Oracle 12c RDBMS. It seems that Oracle 12c system far more sophisticated/feature-rich platform than MS SQL Server – though probably I just don’t know MS SQL Server well enough (need to go through respective for Dummies book?). To some extent there is more to learn here platform wise as it can run both on top of Linux and Windows – so there are far more options and ramifications for deployment and configuring it.\nThe only bad thing about this edition is amount of very obvious typos/editing errors – didn’t expect that from respective brand/publisher. When language errors obvious even for non-native speaker it’s not what you want to allow as respective publisher I guess.

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How to: locate Oracle network configuration file (TNSNAMES.ORA)

TNSNAMES.ORA is a configuration file which stores information about connection strings to Oracle databases. It is located under %ORACLE_HOME%networkadmin (or on Unix server $ORACLE_HOME/network/admin). You may also use set oracle_home command to quickly check the configured value of this environment variable on a Windows machine.\n\nBrowsing through this file allows you to find out such connection properties as protocol, host, port and sid. Alternatively if you know connection name/alias you may use tnsping command to resolve alias and find out all connection parameters (let’s say to use them for configuring connection in Oracle SQL Developer).