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Archive for October, 2011

RIP Ritchie SIR!

October 18th, 2011 No comments

Jobs used c to devlop the mac , even all the major product has base C language and unix, bt aftr the death Sir Ritchie did nt get such media attention as Jobs got 🙁

He was not the owner of any software giant and was not a buisnessman 🙁

RIP SIR Ritchie..You contribution people will remember ever ..forever…

After a long illness, Dennis Ritchie, father of Unix and an esteemed computer scientist, died last weekend at the age of 70.

Ritchie, also known as “dmr”, is best know for creating the C programming language as well as being instrumental in the development of UNIX along with Ken Thompson. Ritchie spent most of his career at Bell Labs, which at the time of his joining in 1967, was one of the largest phone providers in the U.S. and had one of the most well-known research labs in operation.

Working alongside Thompson (who had written B) at Bell in the late sixties, the two men set out to develop a more efficient operating system for the up-and-coming minicomputer, resulting in the release of Unix (running on a DEC PDP-7) in 1971.

Though Unix was cheap and compatible with just about any machine, allowing users to install a variety of software systems, the OS was written in machine (or assembly) language, meaning that it had a small vocabulary and suffered in relation to memory.

By 1973, Ritchie and Thompson had rewritten Unix in C, developing its syntax, functionality, and beyond to give the language the ability to program an operating system. The kernel was published in the same year.
Today, C remains the second most popular programming language in the world (or at least the language in which the second most lines of code have been written), and ushered in C++ and Java; while the pair’s work on Unix led to, among other things, Linus Torvalds’ Linux. The work has without a doubt made Ritchie one of the most important, if not under-recognized, engineers of the modern era.
His work, specifically in relation to UNIX, led to him becoming a joint recipient of the Turing Award with Ken Thompson in 1983, as well as a recipient of the National Medal of Technology in 1998 from then-president Bill Clinton.

UNIX is basically a simple operating system, but you have to be a genius to understand the simplicity – Dennis Ritchie, who was a genius,

Categories: ASE, News Tags:

Sybase wiki created : http://wiki.sybaseblog.com

October 14th, 2011 No comments

Hi All,

Created a wiki for ASE/REP/IQ Standard Operating Practices (SPOs) : http://wiki.sybaseblog.com

Happy Reading.

Thanks

Categories: ASE Tags:

Isolation Level – Summarized.

October 10th, 2011 No comments

Isolation Level ??
=============

Data concurrency: means that many users can access data at the same time.

Data consistency: means that each user sees a consistent view of the data, including visible changes made by the user’s own transactions and transactions of other users.

Isolation : is a property that defines how/when the changes made by one operation become visible to other concurrent operations. Isolation is one of the ACID property.

Lower isolation levels increase transaction concurrency at the risk of allowing transactions to observe a fuzzy or incorrect database state. These incorrect state you need to manage at application design.

4 Isolation Levels:
===================

The ANSI/ISO SQL-92 specifications define four isolation levels:

(1) READ UNCOMMITTED.
(2) READ COMMITTED.
(3) REPEATABLE READ.
(4) SERIALIZABLE.

Lower Isolation level —> Higher concurrency, Data consistancy low, Reducing the locking overhead.
Higher Isolation Level —> Lower Concurrency, High Data Consistancy, Possible More Deadlock in multi user enviorment.

Three preventable phenomena
===========================

P1 (Dirty Read): Transaction T1 modifies a data item. Another transaction T2 then reads that data item before T1 performs a COMMIT or ROLLBACK. If T1 then performs a ROLLBACK, T2 has read a data item that was never committed and so never really existed.

P2 (Non-repeatable or Fuzzy Read): Transaction T1 reads a data item. Another transaction T2 then modifies or
deletes that data item and commits. If T1 then attempts to reread the data item, it receives a modified value or discovers
that the data item has been deleted.

P3 (Phantom): Transaction T1 reads a set of data items satisfying some . Transaction T2
then creates data items that satisfy T1’s and commits. If T1 then repeats its read with the
same , it gets a set of data items different from the first read.

—————————————————————————–
Isolation Level Dirty Read Nonrepeatable Read Phantom Read
——————————————————————————
Read uncommitted Possible Possible Possible
Read committed Not possible Possible Possible
Repeatable read Not possible Not possible Possible
Serializable Not possible Not possible Not possible
——————————————————————————

Should I create an unique index on a column when uniqueness of data is known?

October 1st, 2011 No comments

Question: Should I create an unique index on a column when uniqueness of a column is known?

Suggestion: It is better to create an unique index because it helps the sybase to use some extra optimization when the index is used.

Categories: ASE Tags:

Misconception : sybase query optimizer can not consider index on temporary table if it is created and used in same batch or procedure

October 1st, 2011 No comments

Misconception: sybase query optimizer can not consider index on temporary table if it is created and used in same batch or procedure.

Fact: When an index is created on a temporary table within a proc, sybase performs a runtime recompilation of the proc in order to make use of the index (if appropriate).

Run the sproc with option “set showplan on” and “with recompile” then we can see the multiple copies of sproc if sproc is having index creation on temp tables after temp table population.

Categories: ASE Tags: