what does ACID mean in DBMS?
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In databases, ACID stands for Atomicity, Consistency, Isolation, and Durability. They are considered to be the key transaction processing features/properties of a database management system, or DBMS. Without them, the integrity of the database cannot be guaranteed. In practice, these properties are often relaxed somewhat to provide better performance.\n\nIn the context of databases, a single logical operation on the data is called a transaction. An example of a transaction is a transfer of funds from one account to another, even though it might consist of multiple individual operations (such as debiting one account and crediting another). The ACID properties guarantee that such transactions are processed reliably.\n\n* Atomicity refers to the ability of the DBMS to guarantee that either all of the tasks of a transaction are performed or none of them are. The transfer of funds can be completed or it can fail for a multitude of reasons, but atomicity guarantees that one account won't be debited if the other is not credited as well.\n\n* Consistency refers to the database being in a legal state when the transaction begins and when it ends. This means that a transaction can't break the rules, or integrity constraints, of the database. If an integrity constraint states that all accounts must have a positive balance, then any transaction violating this rule will be aborted.\n\n* Isolation refers to the ability of the application to make operations in a transaction appear isolated from all other operations. This means that no operation outside the transaction can ever see the data in an intermediate state; a bank manager can see the transferred funds on one account or the other, but never on both—even if she ran her query while the transfer was still being processed. More formally, isolation means the transaction history (or schedule) is serializable. For performance reasons, this ability is the most often relaxed constraint. See the isolation article for more details.\n\n* Durability refers to the guarantee that once the user has been notified of success, the transaction will persist, and not be undone. This means it will survive system failure, and that the database system has checked the integrity constraints and won't need to abort the transaction. Typically, all transactions are written into a log that can be played back to recreate the system to its state right before the failure. A transaction can only be deemed committed after it is safely in the log.\n\nImplementing the ACID properties correctly is not simple. Processing a transaction often requires a number of small changes to be made, including updating indices that are used by the system to speed up searches. This sequence of operations is subject to failure for a number of reasons; for instance, the system may have no room left on its disk drives, or it may have used up its allocated CPU time.\n\nACID suggests that the database be able to perform all of these operations at once. In fact this is difficult to arrange. There are two popular families of techniques: Write ahead logging and Shadow paging. In both cases, locks must be acquired on all information that is updated, and depending on the implementation, on all data that is being read. In write ahead logging, atomicity is guaranteed by ensuring that information about all changes is written to a log before it is written to the database. That allows the database to return the database to a consistent state in the event of a crash. In shadowing, updates are applied to a copy of the database, and the new copy is activated when the transaction commits. The copy refers to unchanged parts of the old version of the database, rather than being an entire duplicate.\n\nAlmost all databases used nothing but locking to ensure they were ACID until recently. This means that a lock must be acquired anytime before processing data in a database, even on read operations. Maintaining a large number of locks, however, resul
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acidity has three different definations.\nLewis Acids - a substance capable of accepting as=n unshared electron from a base to form a dative covalent bond.\nArrhenius Acid - a Hydrogen containing compound that ionises and releases protons, [H+] in an aquous solution,\nBronsted Acid - a substances consisting of molecules or ions which donates protons, [H+].\nif any substances adhere to any of the three conditions, it is an acid. \nthe common theory is the Bronsted theory. this is where the term pH is introduced, where pH means 'potential of H+'. a solution with more H+ ions then OH- ions is an acidic solution. the pH is generally <7. however, this standard varies with temperature, and the concentration of the solute(water). \na general apparatus to determined is the blue litmus paper. it'll turn red on contact with acidic solutions.
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"d"\nA CallableStatement object provides a way to call stored procedures in a standard way for all DBMSs. A stored procedure is stored in a database; the call to the stored procedure is what a CallableStatement object contains. This call is written in an escape syntax that may take one of two forms: one form with a result parameter, and the other without one. (See Section 4, "Statement," for information on escape syntax.) A result parameter, a kind of OUT parameter, is the return value for the stored procedure. Both forms may have a variable number of parameters used for input (IN parameters), output (OUT parameters), or both (INOUT parameters). A question mark serves as a placeholder for a parameter.
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acid has a ph value below 7\nand alkali has a value above 7\n\nAn acid (often represented by the generic formula HA) is traditionally considered any chemical compound that when dissolved in water, gives a solution with a pH of less than 7. That approximates the modern definition of Brønsted and Lowry, who defined an acid as a compound which donates a hydrogen ion (H+) to another compound (called a base). Common examples include acetic acid (in vinegar) and sulfuric acid (used in car batteries). Acids generally taste sour;\n\nIn chemistry, an alkali (from Arabic: al-qaly القالي) is a specific type of base, formed as a carbonate, hydroxide or other basic (pH greater than 7) ionic salt of an alkali metal or alkali earth metal element. The word alkali or the adjective alkaline are frequently used to refer to all bases, since most common bases are alkalis, although strictly speaking this is inaccurate.
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There are many definitions, but the most used is this:\nBases tend to either capture protons (H+) or to release proton-capturing species. \nAcids tend to release protons.\n\npH is just a measure of the amount of protons in a solution. Low pH means a high concentration of H+ (acid solution), and high pH the opposite (alkaline solution).
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less than 7 is Acidic...lower the value more acidic it is.\nAbove 7 it is basic.
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Acidic \n\nbelow 6 acidic above 7 basic
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pH was originally written by Dr Sørensen as PH, and it stands for pondus hydrogenii which means "potential hydrogen". The terminology refers to acidity being due to a predominance of hydrogen ions in an aqueous (water containing) solution.
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The normal rate of acid excretion through the kidneys gives urine a pH that falls between 6.75 and 7.25.\nWhen your body has the mineral reserves that it should, the abundance of minerals will show up in a saliva ph test as a pH reading of 7.0 to 7.50.\nCheck out acid base balance on the Net to find more.
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a) neutral\nb) basic\nc) basic\nd) acidic\ne) acidic if in solution\nf) basic.\n\npH is a scale ranging from 0-14.  7 is the intermediate and a pH of 7 means that the solution is neutral.  If the pH is below 7, then there are more H+ than OH- in the solution.  Hence the solution becomes acidic.  If the pH however is greater than 7, then there is less H+ than OH- in the solution and the solution is basic.\n\nFor the acid H2SO4, when in solution, it will dissociate to form H+ and SO4-.  The H+ gives the acid its acidic property.  Similarly when Ca(OH)2 is dissolved, it dissociates into Ca2+ and OH-.  The OH- gives the compound its basic property.
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"Acid Concentration" is well defined.\nIt means: how many acid molecules per unit volume in the liquid.\n   Or more particularly, how many H+ ions are donated by the molecules in \n a unit volume.\nThat because some acid molecules have 2 or 3 H+ ion to donate.\n\nAcid Strength can mean a couple of different things.\n   a) Is that species of molecule strongly acidic?\n         When comparing acid A to acid B, which one donates its H+ ion \n more easily.\n         HCl in water becomes H+ and Cl- right away,\n           so the H+ is just wandering around in that water, looking for \n some damage to do.\n         So we say "HCl is a strong acid".\n         We also say the Acetic Acid in vinegar is a weaker acid.\n          Its molecules H(C2O2H3) try to keep their H's until somebody \n wants it more than they do.\n         The H+ concentration is less, so the acid does less "damage" or \n reacting with things.\n\n  b) Is that solution strongly acidic?\n         A solution is a bucket of water with some concentration of \n chemicals dissolved in it.\n         A strongly acidic solution must have a high instantaneous \n concentration of free H+ ions,\n             regardless of the concentration of other chemicals.\n         A concentrated solution of a weak acid molecule is still a weakly \n acidic solution.\n\nThere are two independent measures of acidity:\n   - concentration of the supposedly acidic molecule,\n             even if it's keeping 99.9% of it's H+'s to itself.\n   - concentration of free H+ ions.\n          The "-log(base10)" of this concentration is called "pH".\n          pH 4  means 10^-4 molar [H+], which is a weak acid solution\n          pH 1 means 0.1 molar [H+], which is a fairly strong acid solution.\nYou need to pin down both to understand the solution well.\n\n\nA pH 4 weak acid solution could be\n     -   a concentrated solution of a weak acid,\n     -   or a 10,000 times diluted solution of a strong acid molecule.\nA strong acid solution with pH=0 can only be\n         a concentrated solution of a strongly acidic molecule.
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Acidity is a measure of ionization. An acid will dissociate to proton (H+) and the conjugate base (or anion). The more stable the anion is, the stronger the acid. In your example, phenol dissociates to phenoxide anion. This anion is resonance stabilized -ie- the negative charge is spread out from the oxygen to 3 of the ring carbons. In cyclohexanol anion, the charge is not resonance stabilized and the minus charge is firmly placed on the one oxygen atom.
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The weaker the acid, the stronger the conjugate base.  The stronger the acid, the weaker the conjugate base.\n\nBy "strong", we are refering to its ability to dissassociate in water and break into ions.\n\nIt might help if you convert all your pKa values to Ka, or all your Ka values to pKa to make it easier to compare.\nWhat does a high Ka value mean?  What does a low Ka value mean?  How does this compare to your definition of a "Strong" acid/base or a "strong" conjugate acid/conjugate base?
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they are used on database file's and processors as shortcuts to things i aint got no example's but yea =)
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DataBase Management System\n\nAdvantages and Disadvantages of using a DBMS\n\n    *\n      Advantages\n          o additional capabilities\n                + sorting\n                + query\n                + integrity checking \n          o easy access to data\n\n    *\n      Disadvantages\n          o few graphical or statistical capabilities\n          o proprietary formats may limit archival qualityof data\n          o require expertise and resources to administer
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Ok, if I am understanding this properly, access is referring to Microsoft Access?\n\nYou cannot open a dbf file from within Access.
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An acid has a higher concerntration of H+ ions in the solution. The PH scale is based on a logorithimic equation where a PH of 7 is neutral, andything below 7 is acidic and anything above 7 is basic. The conjugate acid is the H part of HX where the X- is the conjugate base. \n\nWikipedia has a great explination: http://en.wikipedia.org/wiki/Conjugate_acid