Rejia Bibin

This should be the mantra in your mind when you start anything. It is not just a statement, but a reality. Many great personalities have proven this fact throughout their life. Devotion, perseverance, and hard work are the three pillars on which success stands strong.

You can definitely crack JEE Main in 2 months. There are no two opinions about it. Nonetheless, you must dedicate each minute in a planned manner. Support from proven JEE coaching centers would amplify the possibilities. Besides guiding you towards the target, they would ensure that you don’t get distracted.

Here we are offering you 10 tips that would act as the blueprint towards your goal; clearing JEE Mains in 2 months’ preparation.

Tip #1.      Buy or Borrow the Selected Books Only

Getting all the books that are meant for JEE Main and spreading them around you is not going to work. The more the books, the bigger the ambiguity. Choose only the best books and buy them (or borrow from the seniors). The top books for JEE Mains preparation will have all the topics covered comprehensively. It is best to discuss with your tutors at the JEE coaching center before procuring the books. Experienced professional tutors will know which are the right guides, journals, and texts that would help you prepare for JEE in two months.

Tip #2.      Draw a Preparation Schedule

Studying until the previous day of JEE Main may not be advisable. The last 5-10 days are for revisions, keeping yourself composed, and contemplating whatever you have studied. Therefore, prepare a study schedule for 50-55 days. Topics with more weightage should be given more time. Consider from the 55th day and count backward, i.e. take the 55th day as day one. The timetable for JEE preparation should include leisure time as well. Sitting and studying continuously will not be productive. Rather it would be counterproductive.

Tip #3.      Understand and Imbibe the Concept

Understanding the core concept and infusing it into your brain is important. With the clutch of the crux, you can answer any question on that topic. JEE will have indirect questions aiming to confuse you.  You should ensure that you will not surrender to those confusing questions. Expect such questions, especially in problems. Practicing difficult problems from old questions would be useful to get a catch of the questions. JEE Mains coaching centers will have practice sessions and frequent tests to equip the students to face any type of question.

Tip #4.      Practice Time Management

Time is the villain in JEE, not the difficult questions. You may be able to answer even the most complex questions. But, in the bargain, you will lose a lot of time. In turn, you might miss out on easy questions and valuable marks. A strategized approach is the key to cracking JEE Mains. The 2 months you have in hand, for preparation, are to be utilized for time management as well. Get help from tutors to improve your time management. Another method to improve the performance is to learn tricks and shortcuts from the tutors. This would reduce the time required for problems phenomenally and you would be able to attend to maximum questions correctly.

Tip #5.      Reduce Negative Marks

Negative marks can play spoilsport. You might have answered the maximum possible questions correctly. Notwithstanding, a few wrong answers can affect your rank. Learn methods to reduce negative marks. The most effective way to reduce negative marks is to avoid answering questions at the last moment. Most of the time, students give the wrong answer in a hurry.

Tip #6.      Make Small Notes

Note down important points. Those would be useful during revisions as well as for remembering key elements of the concepts. Use personalized methods to remember the important concepts. Do not study from anyone else’s notes. It is always better to study from your own notes than from any others do.

Tip #7.      Practice Old Questions

Allocate a specific day for practicing old questions. It would help boost your speed, accuracy, and concentration. You will get a better insight into the most important topics and the weightage by practicing the old questions.

Tip #8.     Mock Tests

Similar to practicing old questions, you must attend as many mock tests online as possible. The mock tests are helpful for understanding your speed, identifying your weak areas, and introducing improvements. Discuss with your tutors if required. They would be able to provide you with methods for improving speed. Further, mock tests would strengthen your confidence.

Tip #9.      Limit Social Media for Two Months

It would be best if you can avoid social media for two months, during the preparation for JEE Main. Since it is not viable in the present scenario, you must limit your social media usage. Earmark a specific timing for social media. Keep the data off during the remaining time of the day. Remember that keeping away from social media, for these two months, is going to transform your life.

Tip #10.   Stay Calm, Be Optimistic

Underpinning of reform: Ijtihad

That is how I came to see him as the John Locke of the Muslim World, who advocated freedom—and supported rebellion against tyrannical rulers.

This thesis must come as a complete surprise to those in the West who have heard of Qutb. For example, in this New York Times Magazine feature in March 2003, Paul Berman argued that Qutb’s philosophy—and his rigorous understanding of Islam—was underpinning the ideological basis of al Qaeda and its affiliates.

As a liberal Muslim, the quality that most appeals to me is Syed Qutb’s use of ijtihad, an Islamic juristic tool that is employed to articulate Islamic legal positions on a specific issue. It uses independent reasoning when traditional Islamic sources are silent on a subject.

Today, liberal and progressive Muslims argue that ijtihad should be employed as a tool to reform Muslim societies.

Beyond the military

Syed Qutb’s key contribution was that he redefined the Islamic ideal of jihad. The traditional understanding of the Islamic principles of Jihad (= struggle) in its military sense was as a war of defense against non-believers.

Syed Qutb argued that not only was Jihad an offensive war, but that it could also be waged against internal enemies—including the state, if it had lost its legitimacy.

Echoing Locke

His call for jihad against illegitimate rulers was contrary to traditional Islamic legal thought, which preferred to elevate stability and order over justice and legitimacy—and expressed strong disapproval of rebellions and armed opposition to state authority.

In his book “Milestones”, (Indianapolis: ATP, 1993)—which was originally written in the 1960s—he writes:

“If we insist on calling Islamic jihad a defensive movement, then we must change the meaning of the word “defense”—and mean by it “the defense of man” against all those forces that limit his freedom.” (Milestones, p. 50)

His emphasis on freedom and the legitimacy of government remind me of the works of John Locke, the 17th century English thinker whose imprint is manifestly clear on American democracy. On the topics of freedom, government and its legitimacy and on rebellion, both Qutb and Locke have similar ideas.

Both Locke and Qutb imagined freedom in the same absolutist terms. The human individual was, by virtue of his divine creation, subordinate to God—and God alone—and therefore was a free agent.

Freedom—more important than government?

Locke starts the chapter on “Slavery” in his “The Second Treatise of Government,” which was written in 1680s, with the following comment:

“The natural liberty of man is to be free from any superior power on earth, and not to be under the will or legislative authoritative of man, but to have only the law of nature for his rule.” (p. 15)

For Locke, freedom was a God-given, inalienable attribute that took priority over civil society. Qutb, who argues that Islam meant freedom from human authority, echoed Locke’s ideas about natural rights as God-given and more important than civil society and government.

Hanging onto freedom

For Qutb, Islam was freedom and Islamic society was the civil society, which takes priority to government (Islamic State). He writes:

“This Din (faith) is a universal declaration of the freedom of man from slavery to other men and his desires, which is also a form of human servitude.” (Milestones, p. 47)

“Its purpose is to free those people who wish to be freed from enslavement to men so that they may serve Allah alone.” (Milestones)

It should not be surprising that, after suffering incarceration and harassment by the state (in this case, the Egyptian government), Qutb came to value freedom as necessary even for the practice of faith. He was living in an authoritarian state that imprisoned him—and then eventually hanged him for his ideas.

Authority by contract

Both Locke and Qutb were deeply concerned about the legitimacy of government. They recognized that governments will necessarily compromise the absolute freedom that individuals enjoy in the state of nature — and both therefore focused on the issue of legitimacy.

For Locke, continued consent was the key to legitimacy. Government that did not rule by consent lost its authority to govern.

Locke saw government as a product of a social contract that would identify the objectives and limits of governmental authority. If governments, whatever their form, transgressed their limits or failed to fulfill the designated objectives, then they became illegitimate and could be dissolved.

Legitimacy by way of ethics

Qutb divided societies into two kinds: Islamic—and ignorant. Ignorant societies were bereft of Islamic principles, values and the Islamic way—and hence illegitimate.

Islamic rhetoric aside, Qutb was essentially seeking a connection between social norms and political norms. He identified this connection between social and political ethics as the key to Islamic legitimacy.

Thus, in a rather laborious manner, he did assert that rulers must govern by the values of those governed in order to be legitimate rulers. When governments, which are formed to reflect and defend the values of society failed to do so, then they lost legitimacy—and could be dissolved or replaced.

Revolutionary rationale

John Locke, for his part, developed a careful case to identify the origins of government and its legitimacy. In the process, he developed the rationale for revolution.

Governments must rule by consent and work only to realize their mandate. When they exceeded their limits, they became tyrannical and must be dissolved. If they resorted to force, then they must be dealt with with force.

Lockean terms for dissolution

John Locke’s justification for the use of force to dissolve illegitimate governments was simple and straightforward. Systematic, not occasional, violation of the social contract merited dissolution. And if dissolution was not possible peacefully, it must be done by force.

This is how he put it in his book “The Second Treatise of Government” (p.124):

“Whenever the legislators endeavor to take away and destroy the property of the people, or to reduce them to slavery under arbitrary power, they put themselves into a state of war with the people who are thereupon absolved from further obedience and are left to the common refuge which God has provided for all men against force and violence.”

Activism against political powers

Unlike John Locke, who saw the role of government essentially as the defender of property and freedom, Qutb argued that the role of the state was to free individuals to pursue their moral values. He lived in the age of socialist authoritarianism—and he desperately sought the freedom to practice his faith.

Syed Qutb believed that tyranny could only be undermined through activism and the use of force. He therefore argued that:

“When they have no such freedom, then it becomes incumbent upon Muslims to launch a struggle through individual preaching as well as by initiating an activist movement to restore their freedom, and to strike hard at all those political powers, that force people to bow to their will and authority, defying the commandments of God, and denying people the freedom to listen to the message of Islam, and to accept it even when they wish to do so.” (Milestones, p. 49)

When liberalism turns to totalitarianism

Surely, what I present here is a liberal reading of Qutb—but it is also a liberal reading of Locke. There are moments when Qutb showed sparks of intolerance and even totalitarian proclivities, but then so did Plato.

Unlike Locke, who only focused on his own society, Qutb also included a polemic against the West.

I am sure if Locke had seen his own society colonized and ravaged by the West—as was the Muslim world by European colonialism—he too would have used some tough words for the colonizers.

Locke, more than anything else, believed in the absolute right of private property. He certainly would not have had any kind words for those who robbed other civilizations of their freedom and their resources, through use of force.

Diverging uses of Qutb

While advancing the notion that there can be an alternate reading of Qutb by Muslim ideologues, I am also suggesting that discourses are what we make of them.

Ideas have impact on reality, but reality too has an impact on the formation of ideas and on how ideas are interpreted and applied.

Some Muslims read Qutb and are motivated to use violence against their regimes and the West—whom they perceive as tyrannical.

But Muslims should read Qutb’s ideas as advocating freedom and responsible governance—perhaps the most important traits missing from many Islamic societies today.

Internal diversity

The different readings of Syed Qutb underscore the diversity within Islam and Muslims. Profiles of Islam and Muslims cannot be painted with broad brushes. Muslim realities, like Muslim thought, are complex, diverse and challenging.

As policymakers in Washington rethink the Muslim World, they must remember that ethno-centric interpretations and sweeping judgements will only enhance misunderstanding and lead to bad policy. Bad things happen because of bad policy.

A sympathetic reading of Qutb reveals him as a philosopher of freedom and justice—and not a philosopher of terror. Similarly, a sympathetic view of the Muslim World will reveal a thirst of freedom and justice and not a penchant for violence or hate.

The Enlightenment—a global movement?

The most important lession that can be drawn from this comparison between Locke and Qutb is the fundamental convergence in basic Islamic principles and enlightenment values.

If you have the opportunity to work in a RAC environment, you probably encountered (or you will encounter soon 🙂 ) this wait event: ‘GC Buffer busy’. We will explore issues leading to excessive waits for this wait events and how to resolve the issue effectively.

What is a GC buffer busy wait?

In a simple sense, GC buffer busy means that the buffer in the buffer cache, that the session is trying to access is already involved in another ongoing global cache operation. Until that global cache operation completes, session must wait. I will explain this with an example: Let’s say that session #1 is trying to access a block of file #7 block ID 420. That block is in the remote cache and so, session #1 opened a BL lock on that block, requested the remote LMS process to send the block, and waiting for the block shipping to complete. Session #2 comes along shortly thereafter and tries to access the same buffer. But, the block is already involved in a global cache operation and so, session #2 must wait for the session #1 to complete GC (Global Cache) activity before proceeding. In this case, Session #2 will wait for ‘gc buffer busy’ wait event with a time-out and repeatedly tries to access that buffer in a loop.

Consider the scenario if the block is a hot block such as segment header, index branch block or transaction table header block etc. In this case, you can see that many such sessions waiting for the ‘Gc buffer busy’ wait event. This can lead to complex wait scenario quickly as few background processes also can wait for ‘gc buffer busy’ event leading to an eventual database hang situation. If you kill the processes, then pmon might need to access that block to do a rollback, which means that pmon can get stuck waiting for ‘gc buffer busy’ waits too.

Few Scenarios

This wait event can occur for many different reasons, including bugs. For example, I encountered a bug in which the index branch block split can cause excessive ‘gc buffer busy’ waits. So, It is not possible to document all scenarios that can lead to gc buffer busy waits. But, it is worth exploring few most common scenarios, and then discuss a mitigation plans for those scenarios. The methods discussed here will be helpful to understand which types of blocks are involved in this issue too.

1. Right hand growth indexes

Typically, applications generate surrogate keys using a sequence based key generation, an example would be employee_id column in the employee table. These types of unique or primary key columns are usually populated using a sequence generated value with a unique constraint on the column. A unique index may be created to support the unique constraint. Although, it is possible to create a non-unique index to support the unique constraint, and that non-unique index also will suffer from the issues similar to its unique counterparts. This problem is related to more about uniqueness of data and locality of new rows, rather than the type of index.

Indexes store sorted (key[s], ROWID) pair, meaning values in the index are arranged in an ascending or descending key column order. ROWIDs in the (key[s], ROWID) pair points to a specific row in the table segment with that index column value. Also, Indexes are implemented as B-Tree indexes. In the case of unique indexes, on columns populated by sequence based key values, recent entries will be in the right most leaf block of the B-Tree. All new rows will be stored in the right most leaf block of the index. As more and more sessions insert rows in to the table, that right most leaf block will be full. Oracle will split that right most leaf block in to two leaf blocks: One block with all rows except one row and a new block with just one row. (This split, aka Index 90-10 split, needs to modify branch block also ). Now that new leaf block becomes the right most leaf block and the concurrency moves to the new leaf block. Simply put, you can see concurrency issues moving from one block to another block in an orderly fashion.

As you can imagine, all sessions inserting in to the table will insert rows in to the current right most leaf block of the index. This type of index growth termed as “Right Hand Growth” Indexes. As sessions inserts in to the right most leaf block of the index, that index becomes hot block, and concurrency on that leaf block leads to performance issues.

In RAC, this problem is magnified. Sequence cache is instance specific and if the cache is small (defaults to 20), then the right most leaf block becomes hot block, not just in one instance, but across all instances. That hot – right most – leaf block will be transferred back and forth between the instances. If the block is considered busy, then LMS process might induce more delays in transferring the blocks between the instances. While the block is in transit, then the sessions accessing that block must wait on ‘GC buffer busy’ waits and this quickly leads to excessive GC buffer busy waits. Also, immediate branch block of those right most leaf block will play a role in the waits during leaf block splits.

So, how bad can it get? It can be very bad. A complete database hang situation is a possibility. Notice below that over 1000 sessions were waiting for ‘gc buffer busy’ events across the cluster. Application is completely down.

How do you analyze the problem with right hand key indexes?

First, we need to verify that problem is due to right hand indexes. If you have access to ASH data, it is easy. For all sessions waiting for ‘gc buffer busy’ event query the current_obj#. Following query on ASH can provide you with the object_id involved in these waits. Also, make sure the statement is UPDATE or INSERT statements, not SELECT statement[ SELECT statements are discussed below].

In this example, current_obj# is 8366, which we can query the dba_objects to find the correct object_id. If this object is an unique index or almost unique index, then you might be running in to a right hand growth indexes.

If you don’t have access to ASH then, you need to sample gv$session_wait (or gv$session from 10g), group by p1, p2 to identify the blocks inducing ‘gc buffer busy’ waits. Then, map those blocks to objects suffering from the issue.

You can also use my script segment_stats_delta.sql to see the objects suffering from ‘gc buffer busy’ waits. See below for an example use:

How do you resolve ‘GC buffer busy’ waits due to right hand growth index?

In a simplistic sense, You need to reduce the concurrency on the right most leaf block. There are few options to reduce the concurrency, and hash partitioning that unique index (or almost unique index) is a better solution of all. For example, if we convert the unique index as hash partitioned index with 32 partitions, then you are reducing the concurrency on that right most leaf block by 32 fold. Why? In hash partitioning scheme with 32 partitions, there are 32 index trees and inserts will be spread across 32 right most leaf blocks. In contrast, there is just 1 index tree in the case of non-partitioned index. Essentially, Each partition gets its own index tree. Given an ID column value, that row is always inserted in to a specific partition and that partition is identified by applying hash function over the partitioning column.

In the case of non-partitioned index, for example, values from 1000 to 1010 will be stored in the right most leaf block of the index. In the case of partitioned index with 32 partitions, value 1000 will be stored in partition 24, value 1001 will be stored in partition 19, meaning, values are hashed and spread around 32 partitions leading to improved concurrency. This will completely eliminate Right hand Growth index concurrency issue.

Non-partitioned index Hash partitioned index with 2 partitions

So, What is the drawback of hash partitioning indexes?

If your query needs to do range scan with a predicate similar to ‘id between 1000 and 1005’, then the index range scan will need to scan 32 index trees, instead of one index tree as in the case of non-partitioned tables. Unless, your application executes these sort of queries millions of times, you probably wouldn’t notice the performance difference. For equality predicate, such as ‘id=:B1’, this is not an issue as the database will need to scan just one index tree.

Let’s discuss about reverse key indexes too. As Michael Hallas and Greg Rahn of real-world performance group said (and I happily concur), reverse key indexes are evil. If you are in Oracle Database version 10g, you can create a partitioned index on a non-partitioned table. So, If your application is suffering from a right hand growth index contention issue, you can convert the non-partitioned index to a hash-partitioned index with minimal risk. So, there aren’t many reasons to use reverse key indexes in 10g [ Remember that range scan is not allowed in the reverse key indexes either]. But, if you are unfortunate enough to support Oracle 9i database, you can NOT create a partitioned index on a non-partitioned table. If your application suffers from right hand growth index concurrency issues in 9i, then your options may be limited to reverse key indexes (or playing with sequences and code change or better yet – upgrade to 10g).

2. What if the statement is a SELECT statement?

It is possible for the SELECT statement to suffer from gc buffer busy waits too. If you encounter a scenario in which the object is an index and the statement is a SELECT statement, then this paragraph applies to you. This issue typically happens if there is higher concurrency on few blocks. For example, excessive index full scan on an index concurrently from many instances can cause ‘gc buffer busy’ waits. In this case, right approach would be tune the SQL statement to avoid excessive access to those index blocks.

In my experience, gc buffer busy waits on SELECT statement generally happens if you have problems with statistics and execution plans. So, verify that execution plan or concurrency didn’t change recently.

3. Freelists, Freelist groups

What if the object ID we queried in Active Session History belongs to a table block and the statement is an INSERT statement? We need to check to see if that block is a segment header block. If there are many concurrent inserts, and if you don’t use ASSM tablespace, then the inserts need to find free blocks. Segment header of an object stores the free list [ if you don’t use freelist groups]. So, concurrent inserts in to a table will induce excessive activity on the Segment header block of that table leading to ‘gc buffer busy’ waits.

Concurrent inserts in to a table with 1 freelist/1 freelist groups will also have contention in a non-segment header block too. When the session(s) searches for a free block in a freelist, all those sessions can get one or two free blocks to insert. This can lead to contention on that block.

Right approach in this case is to increase freelists, free list groups and initrans on those objects (and might need reorg for these parameters to take effect ). Better yet, use ASSM tablespaces to avoid these issues.

4. Other Scenarios

We discussed just few common issues. But, ‘gc buffer busy’ waits can happen for many reasons. Few of them are: CPU starvation issues, Swapping issues, interconnect issues etc. For example, if the process that opened the request for a block did not get enough CPU, then it might not drain the network buffers to copy the buffer to buffer cache. Other sessions accessing that buffer will wait on ‘gc buffer busy’ waits. Or If there is a network issue and the Global cache messages are slower, then it might induce higher gc buffer busy waits too. Statistics ‘gc lost packets’ is a good indicator for network issues, but not necessarily a complete indicator.

As a special case, if the sequences have been kept with lower cache value, then blocks belonging to seq$ table can be an issue too. Increasing cache for highly used sequence should be considered as a mandatory task in RAC.

Summary

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