Category: Database Administration

Data Development, Database Administration, Databases, SQL

SQL Tips: How to rename a column in a table – Oracle database – Oracle SQL

At times you will need to change the name of a column in an existing table. If you are not changing the data type, it is just one statement / step that needs to be executed. However, I strongly recommend that you also do a backup step, especially if you’re making the change in a production environment, just in case of an unexpected issue.

If you choose to do the backup, you may perform this with a “create-table-as-select” statement in this form:

create table [table_name_backup] as select * from [table_name];

Here is an example of the above statement:

create table EMPLOYEES_BKUP as select * from EMPLOYEES;

Now that the table you are modifying is all backed up, you can proceed to rename the column.

The rename SQL statement would take this form:

alter table [table_name] rename column [existing_column_name] to [new_column_name];

An example of the statement:

alter table EMPLOYEES rename column SEX to GENDER;

Thanks for reading! I hope you found this information useful.

Data Development, Data Governance, Database Administration, Databases

Oracle Error when table or other object has the same name as the schema name

We recently had a situation where a procedure was running fine in 2 environments but was failing in another. During debugging, it was determined that if the schema prefix was removed from the procedure call, it would run fine, otherwise it fails.

The following error was produced:

ERROR at line 1:

ORA-06550: line 1, column 14:

PLS-00302: component ‘MyProcedure’ must be declared

ORA-06550: line 1, column 7:

PL/SQL: Statement ignored

After some research, the DBA found a web post that indicated that this error is generated if you have an object with the same name as the schema.

You can check if you have any such objects by running this SQL command:

SQL> select * from dba_objects where object_name = ‘Your_Schema_Name’;

(of course, where “Your_Schema_Name” is the actual name of your schema)

If you do, then you should rename the object or remove it if it is no longer needed. Of course, if it is a valid object that is being used, you will need to rename it in all the places in which it is being used.

Thanks for reading! Good luck on your data journey!

Business Intelligence Platform, Data Integration, Database Administration, Performance Tuning

BI Application getting ORA-02391 error

Last week we rolled out a new dashboard that uses a new data source.
In one of our BI environments, the application was throwing an error:
“ORA-02391: exceeded simultaneous SESSIONS_PER_USER limit at OCI call OCISessionBegin“

This is an Oracle Database error, and not an error directly from the BI Application.

For the “ORA-02391: exceeded simultaneous SESSIONS_PER_USER limit” error …
The Cause is:   An attempt was made to exceed the maximum number of concurrent sessions allowed by the SESSIONS_PER_USER clause of the user profile.
And the Action for resolution is:   End one or more concurrent sessions or ask the database administrator to increase the SESSIONS_PER_USER limit of the user profile.

Turns out the SESSIONS_PER_USER parameter was set too low; it was set to 3 for the user being used to access the database from the BI application. This error could have also been observed from an ETL tool accessing the database with an ID with the same parameter setting.

One of the DBAs bumped this parameter up to 30 for the user, and that resolved the issue.
We requested for this change to be done on the BI application databases in all the environments – Development, Test, QA, and Production.

Although all seems to be well, we will now monitor to see how many sessions the application is using and if there is any negative impact on the source application. This will allow us to determine if we need to make any other adjustments.

Thanks for reading. I hope you found this information useful.

BI Administration, Business Intelligence Platform, Database Administration, Databases

BI Application getting ORA-00257 Error

One day this week, we got the following error showing up on our BI dashboards.
“ORA-00257: Archiver error. Connect AS SYSDBA only until resolved.”
This is an Oracle database error (which you may guess based on the “ORA”), and not an error directly from BI application.

If you get this error, it means that the database redo logs are filled up, and cannot be archived due to lack of space on the designated archive area or some other issue. In our case, the “some other issue” was caused by some issues with “commvault”, a software application used for data backup and recovery, among other things.

When this happens, if a user tries to connect to the database, such as the BI Application user in our case, the database will not allow the new connection. The only exception is SYSDBA users will be allowed to connect.

If you are not the database administrator (DBA), you will most likely work with your DBA (as we do) to get this error resolved.
After the issue that caused the problem is resolved and the redo logs are cleared, then the database, and therefore the BI application, will allow new connections as normal.

Thanks for reading and I hope you found this helpful.

Data Analysis, Data Development, Database Administration

Connecting to Microsoft SQL Server database from Oracle SQL Developer

If you work primarily with Oracle databases, you may use SQL Developer. But you may also need to connect to Microsoft SQL Server databases and not necessarily want to install a new front-end database tool, such as Microsoft SQL Server Management Studio (SSMS).  You can connect to SQL Server from SQL Developer.

First, download the appropriate JDBC Driver for the version of SQL Server that you need to connect to. Then follow the steps in the video at the link below on the Oracle website.

https://www.oracle.com/technetwork/developer-tools/sql-developer/sql-server-connection-viewlet-swf-089886.html

Good luck.

 

Database Administration, Databases

Work-around Solution for Oracle Database Error ORA-01792: maximum number of columns in a table or view is 1000

When you get this Oracle database error message …

Error message: Caused By: java.sql.SQLSyntaxErrorException: ORA-01792: maximum number of columns in a table or view is 1000

This may be a solution for you …

There is a workaround … set the “_fix_control” parameter to ‘17376322:OFF‘.

You can use one of the following statements to set the parameter:

alter session set "_fix_control" = '17376322:OFF';

or

alter system set "_fix_control" = '17376322:OFF';

More information can be found in the following Oracle Documents –  Doc ID 1956038.1 and Doc ID 1951689.1.

Database Administration, Databases

How to determine your database version for various RDBMS’s: Oracle, SQL Server, MySQL, DB2

Occasionally you may need to check one of your database’s version for the purpose of creating a ticket with the software vendor, for checking compatibility with other software, preparing for upgrades, getting database client software, and other reasons.

Below are commands for identifying the version of your database for a few of the more popular RDBMS’s.  Please keep in mind that these may or may not work on your version of database or type of operating system.

RDBMS_popular_relational_databses

ORACLE

  • SELECT * FROM V$VERSION;

Your output will be something like this …
version_output_oracle

SQL SERVER

Try one of the following:

  • Select “Help -> About” from the SQL Server Management Studio menu.
  • select @@version
  • You may also connect to the server by using Object Explorer in SQL Server Management Studio. After Object Explorer is connected, it will show the version information in parentheses, together with the user name that is used to connect to the specific instance of SQL Server.

MYSQL

Try one of the following:

  • shell> mysql –version
  • mysql> SHOW VARIABLES LIKE ‘%version%’;
  • mysqladmin version  -or- mysqladmin –v

DB2

Try one of the following:

  • SELECT * FROM TABLE(SYSPROC.ENV_GET_INST_INFO());
  • SELECT GETVARIABLE(‘SYSIBM.VERSION’) FROM SYSIBM.SYSDUMMY1;