Oracle Interview Questions - Part-2

26. What is hash cluster?
A row is stored in a hash cluster based on the result of applying a hash function to the row’s cluster key value. All rows with the same hash key value are stores together on disk.

27. When can hash cluster used?
Hash clusters are better choice when a table is often queried with equality queries. For such queries the specified cluster key value is hashed. The resulting hash key value points directly to the area on disk that stores the specified rows.

list of tables in an Oracle database

To list the tables in the schema of the current user:

SELECT table_name FROM user_tables;
or
select * from tab ;

Magic Command to BackUp Putty Sessions

1) Open Run in Windows ( Window + R )
2) Put below command in Run

Get DB2 Version

Method #1. Connect to the database from the command line


 

First time IIS User Setup - DataStage 8.7

Typical users list:

• wasadmin
• isadmin
• db2inst1,db2iadm1
• db2fenc1,db2fadm1
• dasusr1,dasadm1
• xmeta,xmeta (db owner)
• xmetasr (staging area)
• iauser,iadb (db user)
• dsadm,dstage

Selecting DataStage job log results in error: Error Selecting from log file RT_LOG

When trying to view a job log in DataStage Director, an error similar to the following is received:

Error selecting from log file RT_LOGnn
Command was: SSELECT RT_LOGnn WITH @ID LIKE '1NON' COUNT.SU
Error was: Internal data error. File <path_to>/RT_LOGnn/<filename>':
Computed blink of 0xnnnn does not match expected blink of 0xnnnn! Detected within group starting at address 0xnnnnnn!
The error message received indicates that the log file for the job is corrupted.

Oracle Interview Questions - Part-1

1. What are the components of physical database structure of Oracle database?
Oracle database is comprised of three types of files. One or more datafiles, two or more redo log files, and one or more control files.

2. What are the components of logical database structure of Oracle database?
There are tablespaces and database’s schema objects.

3. What is a tablespace?
A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together.

Delete All PuTTY Sessions Together

When you are swapping an old computer with a new computer, you may end-up transferring all PuTTY sessions to new computer. Once you’ve transferred all PuTTY sessions, execute “putty -cleanup” from the command line as shown below.

Execute an SQL script file in SQLPlus - Oracle

To execute a script file in SQLPlus, type @ and then the file name.

SQL > @{file}

For example, if your file was called script.sql, you'd type the following command at the SQL prompt:

SQL > @script.sql

The above command assumes that the file is in the current directory. ( the current directory is usually the directory that you were located in before you launched SQLPlus.)

DataStage-Director: Unable to open DICT 'RT_LOG###'

When attempting to open a job log in Director, user gets the following error message: Error selecting from log file RT_LOG### Error was: Unable to open DICT 'RT_LOG###'. This is because the D_RT_LOG file is missing from the projects directory.

MQ queue naming standards

The naming of the WebSphere MQ queues is an important part of Q replication setup. It may be that your site already has a naming standard for MQ queues, but if it does not, then here are some thoughts on the subject.

Queues are related to Q Capture and Q Apply programs, so it would be useful to have that fact reflected in the name of the queues.

Putty Sessions Time Out due to Inactivity

The ssh client PuTTY can be configured to maintain a connection and not time out due to inactivity.

 

To set up a new connection with "keep alives" to maintain your connection follow the steps below:

1. Open the PuTTy application and navigate to the Options panel.
2. Select Connection
3. In the field Sending null packets to keep session active change the default value from 0 to 1800 (30 minutes)

DataStage Job aborts with error: "The record is too big to fit in a block"

To fix this error you need to increase the block size to accommodate the record size:

1. Log into Designer and open the job.
2. Open the job properties--> parameters-->add environment variable and select: APT_DEFAULT_TRANSPORT_BLOCK_SIZE

How to save User Name in Putty Sessions

1. Clicked on Any Saved Session and Load it 
2. Click Connection > Data in the Category navigation tree.

DataStage Macros Example

Job Design :
 

DataStage Macros

They are built from Data Stage functions and do not require arguments.

A number of macros are provided in the JOBCONTROL.H file to facilitate getting information about the current job, and links and stages belonging to the current job. These can be used in expressions, job control routines, filenames and table names, and before/after subroutines.

Some Parallel transformer Macros are listed here, as said, these can be used in anywhere in job

Failure to connect to DataStage services tier: invalid host name

When you attempt to start one of the Datastage clients, the following message is displayed:

Failed to authenticate the current user against the selected

Domain: Server [servername] not found.

Checks & Solution :

You might be specifying an incorrect name for the computer that is hosting the services tier.

You can check whether the application server is running by attempting to connect to the application server using an Internet browser.