Interview Questions.

Question 1. What Is The Informix-listing@iiug.Org Mailing List?

Answer :

The informix-listing@iiug.Org mailing list is a bi-directional gateway to the comp.Databases.Informix (c.D.I) UseNet information institution. Messages posted to the information institution are forwarded with the aid of mail to subscribers of the mailing list; responses sent to the informix-listing@iiug.Org e-mail address also are posted to the news group; and the gateway manages to hold music of things in order that postings do now not repeat themselves. The mailing list is 'closed' in which you cannot post directly to the listing except you furthermore may join the list. However, you may usually publish to the news group rather; this is fully open and unmoderated.

Question 2. What Rules Exist Regarding Format, Content, Flame Wars, Etc

Answer :

None; that is a information group! That is, there are not any regulations enforced by means of the software. There are periodically discussions on c.D.I about what need to and must no longer be said. This is my FAQ, so it receives my spin on the policies that should be accompanied.

* Format: HTML postings are strongly discouraged; so are MIME postings. Both cause issues with many often used news readers. That method that attachments aren't endorsed both. Also, sending the equal information twice, once in HTML and as soon as in plain text, is downright wasteful.

IBM - VSAM Interview Questions
Question 3. What Is Chunk In Informix?

Answer :

A bite is a bodily part of disk on which Informix shops its data. A bite can be both a raw partition or a file machine file. Informix shows that a bit's call be a symbolic hyperlink to the real chunk. For example, if you are using /dev/rdsk/c6t0d0s1 as a chunk, you can create a symbolic hyperlink named /dev/informix/chunk1 that factors to /dev/rdsk/c6t0d0s1. That way, if there are ever any problems with that disk, you may update the disk with any other one and just change the symbolic hyperlink.

Question 4. What Is Informix Instance?

Answer :

An Informix instance is a single connection to shared memory. It is represented with the aid of one or more on init methods. When Informix is started or stopped, these strategies seem and disappear. Informix used to apply the term "server" while relating to an instance, hence the surroundings variable DBSERVERNAME.

IBM DB2 Tutorial
Question five. What Are The Uses Of Key Value Locking In Informix?

Answer :

The database server uses a concept known as key-value locking to fasten the deleted row. When the database server deletes a row, key values within the indexes for the table are not eliminated at once. Instead, every key value is marked as deleted, and a lock is positioned on the key cost. One of the maximum important uses for key-price locking is to guarantee that a completely unique key stays particular via the cease of the transaction that deleted it.

IBM DB2 Interview Questions
Question 6. Who Conceived And Designed The Informix Database Management System?

Answer :

The Informix database control gadget was conceived and designed by Roger Sippl in the late 1970s. Informix was founded in 1980, went public in 1986, and for a duration all through the Nineties Informix changed into the second one maximum popular database gadget, after Oracle.

Question 7. What Is The Option Or Command Used In Informix For Finding Which Dbspace A Database Resides?

Answer :

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

MySQL Tutorial MySQL Interview Questions
Question 8. Who Developed Informix?

Answer :

IBM released Informix

Question nine. Mention The Database Server Operating Modes Available For Informix?

Answer :

Informix IDS offer following modes:-

Online mode: This is the regular working mode of the database server.
Offline mode?: The database server isn't running. Shared reminiscence isn't always allotted.
Quiescent mode: This is the ordinary running mode of the database server.
Administrators use this mode to carry out preservation capabilities that don't require the execution of SQL and DDL statements. Only the administrator (consumer informix) can get right of entry to the database server.

Single-User mode: This mode is an intermediary mode between Quiescent mode and Online mode?
Administrators use this mode to carry out any maintenance project, which includes duties requiring the execution of SQL and DDL statements. Administrators can also carry out all different functions to be had in Online mode. You can see the modern-day database server mode with the aid of executing the onstat - software from the command.

PostgreSQL Interview Questions
Question 10. What Is Extent In Informix?

Answer :

If a table is designed without specifying extent sizes, Informix makes use of a default of sixteen pages for the primary and 8 pages for every next volume. Extent sizing is accomplished when the desk is to start with created.

MongoDB Tutorial
Question eleven. What Is Informix Binary Large Object?

Answer :

A binary large object, additionally called a blob, is a collection of binary information stored as a single entity in a database control system. Informix invented an alternative backronym, Binary Large Object. Blobs are usually photos, audio or different multimedia gadgets, though every now and then binary executable code is stored as a blob.

MYSQL DBA Interview Questions
Question 12. Explain About Light Scans In Informix?

Answer :

Light scans arise beneath the subsequent situations: The optimizer chooses a sequential scan of the desk. The wide variety of pages in the desk is extra than the wide variety of buffers within the buffer pool. The isolation stage obtains no lock or a shared lock at the desk: Dirty Read (including non logging databases) isolation level Repeatable Read isolation degree if the table has a shared or exclusive lock Committed Read isolation if the desk has a shared lock

IBM - VSAM Interview Questions
Question 13. Can I Ask About Perl, Dbi And Dbd Informix? Other Products?

Answer :

You may ask questions about Perl, DBI and DBD::Informix, however handiest if an IBM or Informix database is concerned, one way or the other -- it isn't always a trendy discussion board for arbitrary questions about Perl. However, there are opportunity boards that you must additionally use, defined inside the product. 

Question 14. Can I Install Informix On A Non-english Version Of Windows Nt?

Answer :

Yes, however you need to put in model 7.30 TC 6 or better.

Question 15. I Think I Screwed Up My Onconfig File, And I Do Not Have A Backup Of It. What Should I Do?

Answer :

If Informix is still online, you could get a brand new onconfig with:

onstat -c >onconfig

If Informix is offline, you could retrieve the settings from the database with:

oncheck -pR
or
oncheck -pP 1 1

IBM AIX 7 Administration Interview Questions
Question 16. Somehow Informix Fails To Go Online. Is There A Way To View What Oninit Is Doing?

Answer :

Yes, you can begin Informix in verbose mode:

oninit -v (this works on NT as well)

Informix will print the whole lot that occurs.

To close the verbose mode: begin a second terminal session (UNIX) or command activate (NT) and execute:

onmode -ky

N.B. Don't close your terminal consultation (UNIX) or command prompt (NT) even as in verbose mode. This will take Informix offline right away.

Question 17. What Can Be Used To Capture An Isam Error From An Informix Odbc Program On Unix?

Answer :

We can use the SQLCA structure to get the ISAM Error.

Sqlca.Sqlerrd[1] holds the ISAM blunders go back code.

We also can use the rgetlmsg() and rgetmsg() library capabilities to gain ISAM error message text.

Java applet Interview Questions
Question 18. What Is Informix Universal Server?

Answer :

Informix Universal Server changed into the brand call given to the nine.X versions of the product; the improve from the Informix Dynamic Server (IDS) 7.X products, skipping the XPS eight.X release numbers. The 9.X server contained some of practical advances (information kind extensibility, DataBlades and so forth), in addition to enhancements to the storage supervisor and SQL processing. The maximum current versions of the Informix line -- 10.X -- are an evolutionary development over the nine.X engine.

IBM DB2 Interview Questions
Question 19. What Is The Size Of Informix Page?

Answer :

The maximum common page length used is 2KB, though some systems uses 4KB web page.

Question 20. Why A Foreground Write In Informix Decrease Performance?Nation The Reason For The Same?

Answer :

foreground writes (FG) have to usually be 0. A foreground write is triggered while a consultation needs to have a page from disk placed into the buffer pool, but there aren't any smooth/loose buffers to be had. In this situation, the sqlexec thread will select a page off the least recently used aspect of an LRU queue, write it out, and mark the page as smooth. This method is time consuming for a consultation and must be avoided.

DB2 SQL Programming Interview Questions
Question 21. How Would You Convert A Secondary Server Into A Primary Server ?

Answer :

EXECUTE FUNCTION assignment(“ha sds primary”,”srv_slave”);
If it's miles HDR and the secondary will become the new standalone server: onmode -d standard
Question 22. Explain Checkpoints And Why In nine.4 They Were Better Than In Previous Versions Of The Engine?

Answer :

You are nevertheless using nine.Four ? It’s out of help for 3 years … . We upgraded from 10.00FC6 to 11.50FC7 remaining yr.
The first Informix database I started out to administrate changed into IDS 10.00FC4. So my first-class wager is that nine.Four introduced partly non blockading checkpoints (fuzzy checkpoints ?), these being outmoded within the latter versions.
The checkpoint is the moment while Informix will flush the contents from the bufferpool to disks.
Question 23. How Could You Increase The Speed Of Ontape/onbar Backups ?

Answer :

On a platform with speedy cpus, write low overall performance and compresable records, the ontape output may be piped and compressed before getting on disk (less IO write operations).
With onbar, more backup speeds may be achived by:
Increase the number of onbar threads -> BAR_MAX_BACKUP
Increase the buffers utilized by onbar (if reminiscence is to be had) ? BAR_NB_XPORT_COUNT
Use a fast storage for the storage pool (We use onbar + IBM Tivolli Storage Manager)
Consider taking incremental backups
SQLite Interview Questions
Question 24. Can You Explain Pdq Priority?

Answer :

By placing PDQ PRIORITY the DBA can change the query execution priority and increase the number of internal threads spawned by using Informix to fulfill the query. Also, some reminiscence allocation techniques differ upon setting PDQPRIORITY.

MySQL Interview Questions
Question 25. And Why Are These Important ?

Answer :

Monitor effect on device’s CPU:
Instance sys vcpu + Instance consumer vcpu
Locks requests / waits
Active locks
Monitor effect on system’s storage (IO) / reminiscence:
Buffer reads / writes / waits
Page reads / writes /
Disk reads / writes
Logical competition:
lock requests / waits
deadlocks
eventually rollbacks
Monitor instance health & status
Dbspaces overall / used / free space
Checkpoint durations & duration
Sequential scans variety
Number of now not but backup-ed logical logs
Number of active periods
And of course the example on-line log.
 

Question 26. Explain The Purpose Of Optimizer Directives And How/why You Would Use Them

Answer :

A DBA can use directives generally to exchange / take a look at / evaluate the execution plan (charges / blessings) for a query, by means of forcing an index / alternate be part of order / and many others.

MongoDB Interview Questions
Question 27. Why Is Update Statistics Important To A Database?

Answer :

Running update records will replace the gadget catalog facts about the database.
This statistics is utilized by the Informix optimizer to calculate expenses and execution plans for everyday queries. Lack of up to date records about records distributions may additionally result in severely awful plans.
PostgreSQL Interview Questions
Question 28. How Would You Check That A Given Index Is Consistent And Has No Corruption? If Corruption Occurred On A Database What Would Your Process Be?

Answer :

Index (together with database and desk) consistency may be validated with oncheck -cDI database_name:table_name. Preferably with the instance put in quiescent mode.
If just the index is corrupted (and no longer fixable by using oncheck), an alternative can be to recreate the index.
Question 29. An Index Is Reaching A Limitation On The Number Of Pages It Has, Can You Explain Why This Limitation Exists And What Work You Would Do To Get Around It?

Answer :

A dbspace could have one or more partitions. Each partition has a special “header” data inside the first quantity.
The partition header keeps a list of the partition’s extents. If the object retaining the gap in the partition (table / index) has a terrific quantity of extents, the header won't be capable of preserve the overall listing.
Workarounds:
increase first / subsequent volume size and recreate the object
change the web page size -> will bring about a decrease wide variety of extents
recreate the index in a dbspace having a bigger web page size
IBM DataPower Interview Questions
Question 30. What Are The Informix Isolation Levels And Can You Explain Each One ?

Answer :

DIRTY READ: Reads the records without checking if it’s committed or not. No locks are held at some stage in the examine
COMMITTED READ: Reads most effective the dedicated facts. No locks held
REPEATABLE READ: Reads best the dedicated data. A shared lock is held on the rows. Other periods can attain shared locks on those rows, but nobody can get an distinctive lock.
CURSOR STABILITY
Question 31. What Command Would You Use To Move The Physical Log?

Answer :

onparams -p -s -d -y
onmonitor utility
in more recent IDS variations, use the SQL API to regulate the plog place
Question 32. What Are The Sql Joins Available In Informix?

Answer :

INNER JOIN, LEFT / RIGHT OUTER JOIN, FULL OUTER JOIN, CROSS JOIN

Question 33. Explain The Concept Of Fragment Elimination In Informix ?

Answer :

Fragment elimination seems whilst the following conditions are all glad:
A desk is fragmented
The fragmentation formulation doesn’t create overlapping ? Asta oricum nu e permis (overlapping)
A query uses equality clear out on a column used in the fragmentation formula
If the above conditions are met, the Informix engine can skip fragments (statistics isn't searched there) that don’t comply with the question filter out
 

MYSQL DBA Interview Questions
Question 34. Why Do Foreground Writes Decrease Performance ?

Answer :

Whenever Informix sqlexec technique searches for a loose / clean buffer with a purpose to read a web page from the disk into that buffer is called foreground write operation. The overall performance penalty seems when there aren't any loose / easy buffers left, and sqlexec has to look for a much less used buffer, write its content material to disk, clean the buffer and reuse the buffer for a foreground write operation – having the downside of NOT being asynchronous (as chunk writes/lru writes)

Question 35. What Can Be Used To Capture An Isam Error From An Informix Odbc Program On Unix ?

Answer :

If the DBA has a query internal a script / program that connects to an Informix example thru an ODBC connection, and going for walks the question effects in an error, then he can use the TRACE capability, and go back DBINFO(sqlca.Sqlerrd[1,2]).

Question 36. What Are The Options/commands Used Which Dbspace A Database Resides?

Answer :

The DBA can use:
The onmonitor application
oncheck -pe more
A query becoming a member of sysdbspaces and sysdatabases tables positioned within the sysmaster database
IBM AIX 7 Administration Interview Questions
Question 37. What Is A Binary Large Object ?

Answer :

Any object for whom its binary statistics report may be stored and restored with fulfillment right into a database can be considered a BLOB.
As an instance, an ecommerce website can shop the product pictures and films internal a database. But that’s now not a high-quality exercise.
 

Question 38. Explain About Light Scans In Informix ?

Answer :

A light experiment might also arise when Informix internal optimizer makes a decision that the great execution plan might be a sequential test (awful query selectivity, loss of indexes…). In this example, if the optimizer similarly makes a decision that the facts set attributable to the query will no longer fit in the buffer pool, it's going to skip it. The result is a light test.

Question 39. What Is An Informix Instance?

Answer :

A series of informix processes in charge of:

Informix shared memory systems
Receive user consultation connection, and places them in touch with the information
Gather statistics information
Allow backup / recuperation actions
Interact with the person periods
At the OS stage, an example may be “visible” as one ore extra oninit procedures + reminiscence structures + disk / staying power structures
Question 40. What Is An Extent In Informix?

Answer :

In Informix, the smallest unit containing records is the “page”. A continuous institution of pages form an extent

Java applet Interview Questions
Question 41. What Are The Database Server Operating Modes Available For Informix? Explain Each.

Answer :

ONLINE : instance is up & strolling, permitting connections from all of the users (that have the necessary offers)
OFFLINE: example is down. No connections to the database allowed
SINGLE USER: instance is up & jogging, however best user informix can get admission to the database. Useful whilst DBA wants to near all of the user sessions, perform some project and produce the example in multi user mode
QUIESCENT: Similar with SINGLE USER mode, useful for renovation undertaking (healing / recuperation of a corrupt or offline dbspace chew)
 

Question 42. What Is A Chunk In Informix ?

Answer :

The “bite” is a record containing informix database records (or a subset of that facts). In may be a report on a internal disk (cooked record) or a uncooked tool (from a SAN platform or inner disks/arrays).

DB2 SQL Programming Interview Questions