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When you enable the automatic indexing on an array, Oracle maintains an index structure to improve the access time of an element. The ARRAY class contains the following methods to support automatic array indexing: public throws public throws synchronized void setAutoIndexing (boolean enable, int direction) SQLException; synchronized void setAutoIndexing(boolean enable) SQLException;

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You can check Session variables in this event for userspecific settings, or create a Session variable to use when your handler executes For example, let s assume that there s a requirement to log how many Session variables are created on a given request It s possible that they can be created in a Page Load event, in a control-specific event trap on a page, or in a preprocessor like PreRequestHandlerExecute To know how many have been created, you ll need to know how many existed at the beginning of the request You can use AcquireRequestState to count them and squirrel this count away: private void HttpAppBase_AcquireRequestState(object sender, EventArgs e) { HttpContext ctx = HttpContextCurrent; if (ctxHandler is ISessionCounter) ((ISessionCounter)ctxHandler)SessionVarCount = ctxSessionKeysCount; } First you acquire a reference to the request context.

Sharing of data: Any number of applications with the appropriate access rights can connect to your database and read the data stored within all without the need to worry about containing the logic to extract this data As you will see shortly, applications use various query languages (most notably SQL) to communicate with databases..

The direction parameter gives the array object a hint. You should specify this parameter to help the JDBC driver determine the best indexing scheme. It can take the following values: ARRAY.ACCESS_FORWARD ARRAY.ACCESS_REVERSE ARRAY.ACCESS_UNKNOWN The default value for the direction parameter is ARRAY.ACCESS_UNKNOWN. Auto-indexing is disabled by default. It makes sense to enable auto-indexing for ARRAY objects when random access of array elements may occur. In the next section, we will benchmark the impact of auto-indexing and auto-buffering on retrieval of array objects.

A logical organization of data: You can write new applications that work with the same data without having to worry about how the data is physically represented and stored. On the basic level, this logical structure is given by a set of entities (data tables) and their relationships. Avoiding data redundancy: Having all requirements from each consuming application up front helps to identify a logical organization for your data that minimizes possible redundancy. For instance, you can use foreign keys instead of duplicating pieces of data. Data normalization is the process of systematically eliminating data redundancy, a large but essential topic that we don t consider in this book. Transactions: Reading from and writing to databases occurs atomically, and as a result two concurrent transactions can never leave data in an inconsistent, inaccurate state. Isolation levels refer to the specific measures taken to ensure transaction isolation by locking various parts of the database (fields, records, tables). Higher isolation levels increase locking overhead and can lead to a loss of parallelism by rendering concurrent transactions sequential; on the other hand, no isolation can lead to inconsistent data. Maintaining data integrity: In other words, databases make sure that the data stored within is accurate. Having no redundancy is one way to maintain data integrity (if a piece of data is changed, it is changed in the only place it occurs; thus, it remains accurate); on the other hand, data security and transaction isolation are needed to ensure that the data stored is modified in a controlled manner.

In this section, we compare the three methods of data retrieval (getArray(), getOracleArray(), and getResultSet()) we covered earlier with and without auto-buffering and auto-indexing. Note that, unfortunately, it not easy to compare memory consumption due to the way JVM works, so we will only compare elapsed times. In real life, you should use a tool such as JProbe (see http://www.quest.com/jprobe/index.asp) to compare the memory consumption of various alternatives as well to get a more balanced perspective. For sample data for our benchmark, we will populate the table number_varray_table we created in the section Creating the Schema for Collections of Built-in Types with 10,000 numbers as follows: benchmark@ORA10G> declare 2 l_varray_of_numbers varray_of_numbers; 3 begin 4 l_varray_of_numbers := varray_of_numbers(); 5 l_varray_of_numbers.extend(10000);

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