Interview Questions
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1.What is Informix Binary Large Object?

A binary large object, also known as a blob, is a collection of binary data stored as a single entity in a database management system. Informix invented an alternative backronym, Binary Large Object. Blobs are typically images, audio or other multimedia objects, though sometimes binary executable code is stored as a blob.

2.What is extent in Informix?

If a table is designed without specifying extent sizes, Informix uses a default of 16 pages for the first and 8 pages for each subsequent extent. Extent sizing is done when the table is initially created.

3.Explain about light scans in Informix?

Light scans occur under the following conditions: The optimizer chooses a sequential scan of the table. The number of pages in the table is greater than the number of buffers in the buffer pool. The isolation level obtains no lock or a shared lock on the table: Dirty Read (including non logging databases) isolation level Repeatable Read isolation level if the table has a shared or exclusive lock Committed Read isolation if the table has a shared lock

4.Mention the database server operating modes available for Informix?

Informix IDS provide following modes:-

  • Online mode ->This is the normal operating mode of the database server.
  • Offline mode? -> The database server is not running. Shared memory is not allocated.
  • Quiescent mode -> This is the normal operating mode of the database server. Administrators use this mode to perform maintenance functions that do not require the execution of SQL and DDL statements. Only the administrator (user informix) can access the database server.
  • Single-User mode -> This mode is an intermediary mode between Quiescent mode and Online mode? Administrators use this mode to perform any maintenance task, including tasks requiring the execution of SQL and DDL statements. Administrators can also perform all other functions available inOnline mode. You can see the current database server mode by executing the onstat - utility from the command.

5.Who developed informix?

IBM released Informix

6.What is the option or command used in Informix for finding which dbspace a database resides?

from command line# onmonitor ->Logical-Logs->Databases

7.Who conceived and designed the Informix database management system?

The Informix database management system was conceived and designed by Roger Sippl in the late 1970s. Informix was founded in 1980, went public in 1986, and for a period during the 1990s Informix was the second most popular database system, after Oracle.

8.What are the uses of key value locking in Informix?

he database server uses a concept called key-value locking to lock the deleted row. When the database server deletes a row, key values in the indexes for the table are not removed immediately. Instead, each key value is marked as deleted, and a lock is placed on the key value. One of the most important uses for key-value locking is to assure that a unique key remains unique through the end of the transaction that deleted it.

9.What is Informix instance?

An Informix instance is a single connection to shared memory. It is represented by one or more on init processes. When Informix is started or stopped, these processes appear and disappear. Informix used to use the term "server" when referring to an instance, hence the environment variable DBSERVERNAME.

10.What is chunk in Informix?

A chunk is a physical portion of disk on which Informix stores its data. A chunk can be either a raw partition or a file system file. Informix suggests that a chunk's name be a symbolic link to the actual chunk. For example, if you are using /dev/rdsk/c6t0d0s1 as a chunk, you could create a symbolic link named /dev/informix/chunk1 that points to /dev/rdsk/c6t0d0s1. That way, if there are ever any problems with that disk, you could replace the disk with another one and just change the symbolic link.

11.Can I ask about Perl, DBI and DBD Informix? Other products?

You may ask questions about Perl, DBI and DBD::Informix, but only if an IBM or Informix database is involved, somehow -- it is not a general forum for arbitrary questions about Perl. However, there are alternative forums that you should also use, described in the product. However, those locations have changed over time, so you should be aware of the official home,, which contains pointers to how to subscribe to the dbi-users at (anti-spammed) mailing list. Note that (as of 2005-03-01 and v2005.01) the email address for DBD::Informix support is dbd.informix at (anti-spammed).

12.What Rules Exist Regarding Format, Content, Flame Wars, etc

None; this is a news group! That is, there are no rules enforced by the software. There are periodically discussions on c.d.i about what should and should not be said. This is my FAQ, so it gets my spin on the rules that should be followed.

* Format: HTML postings are strongly discouraged; so are MIME postings. Both cause problems with many frequently used news readers. That means that attachments aren't encouraged either. Also, sending the same information twice, once in HTML and once in plain text, is downright wasteful.

13.What is the mailing list?

The mailing list is a bi-directional gateway to the comp.databases.informix (c.d.i) UseNet news group. Messages posted to the news group are forwarded by mail to subscribers of the mailing list; responses sent to the email address are also posted to the news group; and the gateway manages to keep track of things so that postings do not repeat themselves. The mailing list is 'closed' in that you cannot post directly to the list unless you also subscribe to the list. However, you can always post to the news group instead; that is fully open and unmoderated.

14.Can I install Informix on a non-English version of Windows NT?

Yes, but you need to install version 7.30 TC 6 or higher.

15.I think I screwed up my onconfig file, and I do not have a backup of it. What should I do?

If Informix is still online, you can get a new onconfig with:
onstat -c >onconfig
If Informix is offline, you can retrieve the settings from the database with:
oncheck -pR
oncheck -pP 1 1

16.Somehow Informix fails to go online. Is there a way to view what oninit is doing?

Yes, you can start Informix in verbose mode:
oninit -v (this works on NT as well)
Informix will print everything that happens.
To close the verbose mode: start a second terminal session (UNIX) or command prompt (NT) and execute: onmode -ky
N.B. Don't close your terminal session (UNIX) or command prompt (NT) while in verbose mode. This will take Informix offline immediately.

17.Mention some of the temporary objects in Informix?

Question How does Informix use temporary dbspaces according to database logging mode, SQL statement WITH NO LOG, temp dbspace parameters settings, etc.? Answer INTRODUCTION IBM® Informix® Dyn...

18.Mention the three major components in Informix Dynamic Server on UNIX system?

Shared memory, processes, disk space.

19.What can be used to capture an ISAM error from an Informix ODBC program on UNIX?

We can use the SQLCA structure to get the ISAM Error.sqlca.sqlerrd[1] holds the ISAM error return code. We can also use the rgetlmsg() and rgetmsg() library functions to obtain ISAM error message text.

20.What is Informix Universal Server?

Informix Universal Server was the brand name given to the 9.X versions of the product; the upgrade from the Informix Dynamic Server (IDS) 7.X products, skipping the XPS 8.X release numbers. The 9.X se...

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