CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a non-provisional application and claims the benefit of and priority to co-pending, commonly assigned U.S. Patent Application No. 60/990,185 entitled “DATA REDUCTION FOR OPTIMIZING AND TESTING”, filed on Nov. 26, 2007, the entire disclosure of which is herein incorporated by reference for all purposes. 
     
    
     COPYRIGHT NOTICE 
       [0002]    A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
       BACKGROUND 
       [0003]    Today, many large and medium sized companies have to manage vast amounts of data for an extended period of time. In one example, a company may maintain benefits data (insurance numbers, participants, social security numbers, account numbers, investments, portfolio value, etc.) for thousands of employees due to legal requirements or contractual obligations. In other examples, a different company may maintain purchasing and order data for millions of customers going back several years. Thus, for companies storing such voluminous data, it is necessary to operate and manage multi-terabyte databases. 
         [0004]    These databases require great amounts of physical storage. The physical storage costs great sums of money to acquire, maintain, and operate. In some instances, a test database is also required to verify the function of different changes to the database or for other reasons. The test databases are a copy of at least a portion of the main database, also referred to as the production database. The test databases are also very costly to create because the test databases often require the same equipment and resources. Compounding the expense, companies generally need multiple copies of the main production database to test functionality of applications, performance of application programs, or upgrades to recent releases, for example. The several copies of the databases further increase the need for physical space to house the equipment and increase the associated costs. In extreme cases, the production databases are simply too large to obtain enough physical space to replicate and test the databases. 
         [0005]    In general, companies try to replicate only a portion of the production database to minimize the costs associated with the test database. However, these test databases having a cross-section of the production database do not reasonably approximate the characteristics of a very large production database. For good test results, the performance characteristics are maintained for various application programs. For example, to test a benefits application, the test database needs to retain the historical distribution of benefits data for employees going back multiple enrollment cycles. 
         [0006]    It is in light of these and other considerations that the present application is being presented. 
       SUMMARY 
       [0007]    It is desirable to provide a test database which allows companies to reduce data storage costs and which can be easily and efficiently replicated and managed at a relatively low cost to those companies. 
         [0008]    Embodiments presented herein provide a testing database instance, which is smaller than the database upon which the testing database is derived. In embodiments, statistics about a production database are gathered. Parameters to be extracted may be determined from the statistics, which can be used to store data only near the endpoints of the distribution (and/or at other key locations). In this way, a substantial amount of data skew is retained in a much smaller instance of the production database, allowing for easier performance testing, upgrade testing, etc. Using the statistics, the testing database is created. Thus, the testing database can be efficiently replicated and maintained for a very large production database while retaining the characteristics and cross-sectional data. In embodiments, the performance characteristics are maintained in order to provide for proper testing of the production database for various application programs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Various embodiments in accordance with the present disclosure will be described with reference to the drawings, in which: 
           [0010]      FIG. 1  is a block diagram of an embodiment of a system for creating testing database; 
           [0011]      FIG. 2  is a block diagram of an embodiment of a software and/or hardware system for creating testing databases; 
           [0012]      FIG. 3  is a graphical representation of a database having data skew; 
           [0013]      FIG. 4  is a flowchart illustrating a method for replicating data from a production database; 
           [0014]      FIG. 5  is a block diagram of an embodiment of a computer network that can be used to replicate databases; and 
           [0015]      FIG. 6  is a block diagram of an embodiment of a computer system that can function in one or more embodiments to create a testing database. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Systems and methods in accordance with various embodiments overcome the aforementioned and other deficiencies in existing database replication, maintenance, and/or testing systems. Embodiments provide for the replication of only those portions of the data necessary for testing and other such purposes which allows a smaller set of data to be maintained and utilized. The embodiments presented herein lowers cost and improves efficiency, while maintaining acceptable test accuracy and performance. 
         [0017]    In embodiments, a database administrator (DBA) creates one or more copies of the production database. One or more of the production database copies can be purged using a purge program. A purge program can purge data according to a variety of parameters associated with the application. In embodiments, the purged information is not necessary for testing the application. The application is, in embodiments, a use or system that stores, retrieves, and uses the data in the production database. For example, if the data in the database represents benefits data, the application is a benefits application. In another example, a database storing ordering data is used by an ordering application. The parameters may be associated with how the application uses the data, statistics or characteristics that are important to the data and/or the application, what test is to be performed on the data, etc. 
         [0018]    Embodiments of the purge program can purge data considering the data skew or performance characteristics of the production database. Hence, the test environment database better represents the function and structure of the production database. Thus, conducting performance tests on the copied instances yields similar or the same results as a test that could be performed on the production database—issues with upgrades or changes to the database can therefore be consistently reproducible. 
         [0019]    Embodiments of the system described herein scale down the volume of the testing database while preserving the data that is primarily responsible for distribution and load issues. The system embodiments provide other advantages. Notably, the system is able to shrink the instance down, such as from multiple terabytes to a few hundred gigabytes and is able to ensure that index maintenance/backups are workable even on lower end machinery. Such an approach to reproducing the production database can preserve segment and tablespace level settings. 
         [0020]    A block diagram of a system  100  that can generate a test database is shown in  FIG. 1 . A client device  102  is, in embodiments, hardware and/or software (for example, a personal computer or terminal) operable to accept inputs from or present information to a database administrator. The client device  102  can communicate with an appropriate server  106  via a network  104 . The server  106  is hardware and/or software operable to communicate with the client device  102 , interface with the database(s)  110  and/or  112 , and/or execute the replication program  108 . The network is, in embodiments, any hardware and/or software operable to allow communication between the one or more components of system  100 . For example, the network is an intranet or the Internet. 
         [0021]    A database replication program  108  can execute on the server  106 . The replication program  108  is, in embodiments, a software program operable to extract data from a production database  110  and generate a testing database  112  from the production data. The production database  110  and/or testing database  112 , in embodiments, is any hardware and/or software operable to store, retrieve, or execute actions on one or more items of data. The production database  110  and/or testing database  112  may be a relational database, a flat file, or other type of database. While in some instances the testing database  112  (or other instance of the production database) and production database  110  might have a common owner on a common network, in some embodiments, the production database  110  might be owned and maintained by a separate entity on a separate network from the testing database  112 . In embodiments, there may be one or more production databases  110 , as represented by the ellipses  114 . Likewise, there can be one or more testing databases, as represented by ellipses  116 . The one or more testing databases  112  may not be similar as each testing database  112  may different portions of the production database  112  created to analyze a particular application with predetermined and different parameters. The production database  110  and/or testing database  112  can include a number of distributed databases, a database system, data repositories, or any of a number of different ways to store and manage related data for an entity. 
         [0022]    An embodiment of a replication program  200  is shown in  FIG. 2 . In embodiments, the replication program  200  is the same or similar to replication program  108  ( FIG. 1 ). The replication program  200  comprises one or more components, which may be software modules, objects, or other software components. In other embodiments, the components are embodiments in hardware, for example, specially-designed circuitry in an application specific integrated circuit (ASIC) or field programmable gate array (FPGA). 
         [0023]    In embodiments, the replication program  200  includes a parameter determination component  204 . The parameter determination component  204  can support the input of an identity of one or more parameters associated with an application  206 . The parameter determination component  204  can receive an identification of an application or process  206 . In embodiments, the parameters are manually identified for the parameter determination component  204 . In other embodiments, the parameter determination component  204  analyzes the application or process  206  with the associated production database  214  to determine the parameters. The parameter determination component  204  can provide the identities of one or more parameters to the optimizer component  202  to determine which parameters to extract from the production database  214  to create the test database  220 . 
         [0024]    In one embodiment, the application  200  includes, or makes calls into, an optimization application  202  (also referred to as the optimizer). In embodiments, the optimizer  202  determines a data distribution function. For example, the optimizer  202  is able to interpret data skew by examining the value endpoints of the production data  214  copied into the testing database  220 . Data skew is the characteristic in a data set where the data does not appear as a normal curve but has more data at one end of the axis. An example of a data set having data skew is shown and explained in conjunction with  FIG. 3 . The optimization application  202  can preserve the high and low numeric/date/other value endpoints in order to keep the data skew intact. In embodiments, the optimization application  202  receives the identification of the main database from the parameter determination component  204  and intelligently uses the provided or determined parameters to clean up data in the test database  220 , excluding the end points. 
         [0025]    The optimizer  202  can comprise a set of query blocks, which include three main functional subsystems: a query transformation engine  208 , an estimator  210 , and a plan generator  212 . The query transformation engine  208 , in embodiments, identifying heuristics, or rules-based algorithms, to provide to the replication component  216  to apply to the query blocks to create the testing database  220 . Some common transformations generated by the query transformation engine  208  include select-join, group-by, and distinct-view merging and materialized view rewrite. 
         [0026]    An estimator  210  can determine a predicted “cost” of issuing one or more queries. For example, a cost model can include system statistics that predict central processing unit (CPU) cycles and/or input/output (I/O) usage with respect to the database system workload. In an example, the Oracle Database 10g predicts a default cost model for CPU plus I/O, in which the cost unit is time. The estimator  210  estimates execution time for a query by estimating the number of I/O operations, the type of I/O operations, and the number of CPU cycles the database will perform while executing the query. In embodiments, the estimates depend on the existence of system statistics in which the estimator  210  converts the number of CPU cycles and the number of I/Os into execution time. Some operations, such as bitmap merge, sort, or hash joins, may not require any I/O but generally all operations include some estimate of CPU cycles. 
         [0027]    In embodiments, the query transformation component  208  and the estimator  210  inform the creation of the testing database  220 . A plan generator component  212  creates a plan for creating the testing database  220 . The plan generator  212  can determine which queries to run, how many queries to run, how to delete data retrieved, etc. The plan generator  212 , in embodiments, provides the plan to the data replication component  216 . 
         [0028]    An example of an optimizer  202  (also referred to as the optimization program) is the optimizer contained in Oracle Database 10g, available from Oracle Corporation. The optimizer  202  can include a cost-based optimizer (CBO) component that has two modes: a “normal” mode and a tuning mode that is invoked by SQL Tuning Advisor (and many other Oracle Database 10g advisors, such as the SQL Access Advisor). The SQL Tuning Advisor is a tool for DBAs that invokes the tuning mode of the CBO to perform a more comprehensive analysis of problematic queries, and generates recommendations about how to achieve the fastest access to the data. One of the possible artifacts of this process is the generation of a SQL Profile, which is an object that can be persisted to the data dictionary if accepting the recommendation, and that is used by the CBO (i.e., during runtime operations in normal mode) to augment the statistics used to generate plans. 
         [0029]    The replication program  200 , in embodiments, can access scripts  218 . Scripts  218  may be other programs, software modules, objects, algorithms, or other components that can analyze the production database  214  and/or the test database  220 . The scripts  218  can determine the values for the parameters provided by the parameter determination component  204 . The scripts  218  can provide details on the data distribution, value end points, and parameters. 
         [0030]    The replication program  200 , in embodiments, comprises a data replication component  216 . In embodiments, the data replication component  216  receives the data distribution function from the optimizer  202 . The data replication component  216  can extract data from the production database  214  in accordance with the data distribution function. The data replication component  216  can include the functions or component necessary to perform the queries provided by the optimizer  202 , delete data from the replicated production database  214 , store the testing database  220 , etc. Thus, the data replication component  216  can create an instance of the production database  214 . For example, when the data replication component  216  of the replication program  200  is run with a set of parameters for a benefits application, the result is an identification of persons whose benefits data needs to be deleted from the production database  214  to create the testing database  220 . The data replication component  216  can be run multiple times with various parameters, resulting in deletion of data as required. 
         [0031]    In embodiments, the end result of every run is a report  222 . The report  222 , in one embodiment, allows for monitoring of the replication process to ensure that value endpoints are being retained and data is being purged as expected. The data replication component  216  can utilize multiple threads to perform the task of deletion and, thus, is faster and more efficient. 
         [0032]    The data replication component  216  deletes data, in one embodiment, by removing identifiers, such as “PersonIDs” and related information. For example, the data replication component  216  can delete benefits information for a benefits application where the benefits information is not involved in the first or last enrollment year, and with PersonIDs not being at the beginning or the end, numerically. Thus, the historical distribution of benefits data can be retained for a person going back years or multiple enrollment cycles. An example of such a benefits application is Oracle Advanced Benefits®, which is an integrated part of Oracle Human Capital Management® (HCM) component of the Oracle E-Business Suite® of applications, available from Oracle Corporation of Redwood Shores, Calif. Oracle Advanced Benefits® supports various aspects of benefits functionality, such as managing benefits information of employees, retirees, and their dependents and beneficiaries. Such an application also manages the costs incurred and the period for availing benefits. 
         [0033]    A graphical representation of an example  300  of a production database  214  ( FIG. 2 ) is shown in  FIG. 3 . The data  302  is shown having a date of creation for one or more records along the x-axis  306  and the number of records having the specific data of creation along the y-axis  304 . As shown in the example, the data  302  has a skew as more data is further to the right of the x-axis  306 . In one embodiment, the replication program  200  ( FIG. 2 ) retains approximately 10% of the data at each endpoint, to maintain the skew in the production database  214  ( FIG. 2 ). The data replication component  216  ( FIG. 2 ) retains, for example, sections  308  and  310 . Thus, the replication program  200  ( FIG. 2 ) manages to purge 80-90% of original data in creating the testing database  220  ( FIG. 2 ) while maintaining the original data skew as much as possible. 
         [0034]    The resultant testing database  220  ( FIG. 2 ) is much lighter than the production database  214  ( FIG. 2 ) and easier to manage. The testing (or replicated) database  220  ( FIG. 2 ) then can be used for various purposes, for example, obtaining a volume database from customers with similar performance characteristics. Such a light weight testing database  220  ( FIG. 2 ) also can be used for performance testing and reproduction of performance issues, as well as to obtain performance metrics between major application releases or major functionality changes. A testing database  220  ( FIG. 2 ) can also be used to measure in-house performance metrics, such as for upgrade acceptance. The replication program  200  ( FIG. 2 ) can thus purge data intelligently resulting in smaller replicated databases with similar performance characteristics as the main database. These replicated databases  220  ( FIG. 2 ) can be used to reproduce performance issues and are easier to maintain and run on lower end hardware. 
         [0035]    Application teams (e.g., those groups of people that utilize the data for a function or purpose) can utilize copies of critical customer databases that are supported for functional or performance issues in smaller sizes than the actual databases, thus resulting in reduced disk costs and easier maintenance. Application teams can use these databases for performance benchmarking, such as to evaluate upgrades or test major functional changes, from a performance perspective, against customer data distributions. 
         [0036]    An example of a method  400  for creating a testing database is shown in  FIG. 4 . In embodiments, the method  400  is executed by the replication application  200  ( FIG. 2 ), wherein the replication application  200  ( FIG. 2 ) includes two separate programs (or two functional modules within the same program). 
         [0037]    Identify operation  402  identifies the production database  214  ( FIG. 2 ) to replicate. In embodiments, a user or administrator provides the identity of the production database  214  ( FIG. 2 ) by providing a database identifier or providing some indication of the database. In other embodiments, the user provides an identity of the process or application program  206  ( FIG. 2 ) to be executed and the replication program  200  determines the production database  214  ( FIG. 2 ) by an association with the application program or process  206  ( FIG. 2 ) provided by the replication program  200 . 
         [0038]    Obtain operation  404  obtains statistics on the data distribution. In embodiments, the replication program  200  ( FIG. 2 ) analyzes the production database  214  ( FIG. 2 ). The optimizer  202  ( FIG. 2 ), in embodiments, obtains statistics on the type of data distribution for the data in the identified production database  214  ( FIG. 2 ). Determine operation  406  determines the parameters to be used or provided. In embodiments, the replication program  200  ( FIG. 2 ) determines the parameters to use to create the testing database  220  ( FIG. 2 ). The optimizer  202  ( FIG. 2 ) can provide the statistics to a plan generator  212  ( FIG. 2 ) to determine parameters. 
         [0039]    Extract operation  408  extracts the determined parameters from the production database  214  ( FIG. 2 ). In embodiments, the optimizer  202  ( FIG. 2 ) provides the parameters to a data replication component  216  ( FIG. 2 ) to extract the parameters. The plan generator  212  ( FIG. 2 ), in alternative embodiments, provides the data replication component  216  ( FIG. 2 ) with a plan to extract the components. The data replication component  216  ( FIG. 2 ) copies the data from the production database  214  ( FIG. 2 ), and, in embodiments, the data replication component  216  ( FIG. 2 ) stores only those necessary parameters to the testing database  220  ( FIG. 2 ). In another embodiment, the data replication component  216  ( FIG. 2 ) copies all the data from the production database  214  ( FIG. 2 ) and then deletes one or more parameters from the testing database  220  ( FIG. 2 ). The deletion of the appropriate data can shrink the size of the database. Store operation  410  stores the database. In embodiments, the data replication component  216  ( FIG. 2 ) stores the testing database  220  ( FIG. 2 ). In this way, the replication program  200  ( FIG. 2 ) stores only parameters near the endpoints of the distribution in the testing database  220  (as described in conjunction with  FIG. 3 ). A substantial amount of data skew is retained in a much smaller copy of the customer database. As discussed above, such an approach allows for easier performance testing, upgrade testing, etc., on the replicated databases. These processes can be used generically across whatever database product is used, with minimal, if any, coding changes. 
         [0040]    The replication program  200  ( FIG. 2 ) can examine the way that the customer database works technically rather than from an application and functional distribution perspective. An optimizer  202  ( FIG. 2 ) can evaluate the production database  214  ( FIG. 2 ) based on distribution statistics. In embodiments, an algorithm is used to preserve (in accordance with the distribution statistics for the optimizer  202  ( FIG. 2 )) a top and bottom portion of the distribution. Thus, the middle range of the data can be deleted, preserving the reproducibility of the customer data while significantly shrinking the size of the instance of the data. The top and bottom percentages are important because a lot of the issues faced by applications are due to a historical data distribution, including data stretching back over several years. 
         [0041]    For other applications or distributions, the application may determine the amount to keep as necessary, which can be as little as 1% or 5%, or as much as 15% or 20% at each end. In other embodiments, the optimizer  202  ( FIG. 2 ) may decide to keep a greater percentage near one of the endpoints. Other embodiments might look to other factors, such as determining which tables have the heaviest load and then looking at the distributions for those tables, or weighting those tables more when determining the data to be retained. Such factors may vary based on the application, as for certain applications problems tend to occur only on a certain type of table. The percentages to be kept also can be determined based in part on a capacity or load of the testing database  220  ( FIG. 2 ). 
         [0042]    SQL profiles use sampling to collect additional information; partial execution techniques to verify and adjust cost estimates; and execution history information for the SQL statement to modify parameter settings, if needed. In one embodiment, SQL queries (or other such queries) submitted to the database engine first run through a parser, which checks syntax and analyzes semantics. The result of this run-through is a set of query blocks that is sent to the optimizer  202  ( FIG. 2 ). 
         [0043]    In embodiments, two types of system statistics are gathered including statistics captured without a workload (“noworkload”) and statistics captured with a workload. Noworkload statistics capture I/O system performance, including average I/O seek time and transfer speed, as well as CPU speed. When gathering noworkload statistics, the CBO issues sample reads of different sizes from the database&#39;s data files. The CBO times every read and then uses statistical methods to compute average seek time and transfer speed. This takes from a few seconds to a few minutes. The CBO computes CPU speed in millions of cycles per second. Workload statistics make the CBO aware of the workload. The system statistics captured during workload conditions identify whether the system is I/O- or CPU-bound, and the CBO uses the data to adjust the cost of the plans accordingly. 
         [0044]      FIG. 5  is a block diagram illustrating components of an exemplary operating environment in which various embodiments of the present disclosure may be implemented. The system  500  can include one or more user computers, computing devices, or processing devices  512 ,  514 ,  516 ,  518 , which can be used to operate a client, such as a dedicated application, web browser, etc. The user computers  512 ,  514 ,  516 ,  518  can be general purpose personal computers (including, merely by way of example, personal computers and/or laptop computers running a standard operating system), cell phones or PDAs (running mobile software and being Internet, e-mail, SMS, Blackberry, or other communication protocol enabled), and/or workstation computers running any of a variety of commercially-available UNIX or UNIX-like operating systems (including without limitation, the variety of GNU/Linux operating systems). These user computers  512 ,  514 ,  516 ,  518  may also have any of a variety of applications, including one or more development systems, database client and/or server applications, and Web browser applications. Alternatively, the user computers  512 ,  514 ,  516 ,  518  may be any other electronic device, such as a thin-client computer, Internet-enabled gaming system, and/or personal messaging device, capable of communicating via a network (e.g., the network  510  described below) and/or displaying and navigating Web pages or other types of electronic documents. Although the exemplary system  500  is shown with four user computers, any number of user computers may be supported. 
         [0045]    In most embodiments, the system  500  includes some type of network  510 . The network  510  can be any type of network familiar to those skilled in the art that can support data communications using any of a variety of commercially-available protocols, including without limitation TCP/IP, SNA, IPX, AppleTalk, and the like. Merely by way of example, the network  510  can be a local area network (“LAN”), such as an Ethernet network, a Token-Ring network and/or the like; a wide-area network(WAN); a virtual network, including without limitation a virtual private network (“VPN”); the Internet; an intranet; an extranet; a public switched telephone network (“PSTN”); an infra-red network; a wireless network (e.g., a network operating under any of the IEEE 802.11 suite of protocols, GRPS, GSM, UMTS, EDGE, 2G, 2.5G, 3G, 4G, WiMax, WiFi, CDMA 2000, WCDMA, the Bluetooth protocol known in the art, and/or any other wireless protocol); and/or any combination of these and/or other networks. 
         [0046]    The system  500  may also include one or more server computers  502 ,  504 ,  506  which can be general purpose computers, specialized server computers (including, merely by way of example, PC servers, UNIX servers, mid-range servers, mainframe computers rack-mounted servers, etc.), server farms, server clusters, or any other appropriate arrangement and/or combination. One or more of the servers (e.g.,  506 ) may be dedicated to running applications, such as a business application, a Web server, application server, etc. Such servers maybe used to process requests from user computers  512 ,  514 ,  516 ,  518 . The applications can also include any number of applications for controlling access to resources of the servers  502 ,  504 ,  506 . 
         [0047]    The Web server can be running an operating system including any of those discussed above, as well as any commercially-available server operating systems. The Web server can also run any of a variety of server applications and/or mid-tier applications, including HTTP servers, FTP servers, CGI servers, database servers, Java servers, business applications, and the like. The server(s) also may be one or more computers which can be capable of executing programs or scripts in response to the user computers  512 ,  514 ,  516 ,  518 . As one example, a server may execute one or more Web applications. The Web application may be implemented as one or more scripts or programs written in any programming language, such as Java®, C, C# or C++, and/or any scripting language, such as Perl, Python, or TCL, as well as combinations of any programming/scripting languages. The server(s) may also include database servers, including without limitation those commercially available from Oracle®, Microsoft®, Sybase®, IBM® and the like, which can process requests from database clients running on a user computer  512 ,  514 ,  516 ,  518 . 
         [0048]    The system  500  may also include one or more databases  520 . The database(s)  520  may reside in a variety of locations. By way of example, a database  520  may reside on a storage medium local to (and/or resident in) one or more of the computers  502 ,  504 ,  506 ,  512 ,  514 ,  516 ,  518 . Alternatively, the database  520  may be remote from any or all of the computers  502 ,  504 ,  506 ,  512 ,  514 ,  516 ,  518 , and/or in communication (e.g., via the network  510 ) with one or more of these. In a particular set of embodiments, the database  520  may reside in a storage-area network (“SAN”) familiar to those skilled in the art. Similarly, any necessary files for performing the functions attributed to the computers  502 ,  504 ,  506 ,  512 ,  514 ,  516 ,  518  may be stored locally on the respective computer and/or remotely, as appropriate. In one set of embodiments, the database  520  may be a relational database, such as Oracle 10g, that is adapted to store, update, and retrieve data in response to SQL-formatted commands. 
         [0049]      FIG. 6  illustrates an exemplary computer system  600 , in which various embodiments of the present disclosure may be implemented. The system  600  may be used to implement any of the computer systems described above. The computer system  600  is shown comprising hardware elements that may be electrically coupled via a bus  624 . The hardware elements may include one or more central processing units (CPUs)  602 , one or more input devices  604  (e.g., a mouse, a keyboard, etc.), and one or more output devices  606  (e.g., a display device, a printer, etc.). The computer system  600  may also include one or more storage devices  608 . By way of example, the storage device(s)  608  can include devices such as disk drives, optical storage devices, solid-state storage devices such as a random access memory (“RAM”) and/or a read-only memory (“ROM”), which can be programmable, flash-updateable and/or the like. 
         [0050]    The computer system  600  may additionally include a computer-readable storage media reader  612 , a communications system  614  (e.g., a modem, a network card (wireless or wired), an infra-red communication device, etc.), and working memory  618 , which may include RAM and ROM devices as described above. In some embodiments, the computer system  600  may also include a processing acceleration unit  616 , which can include a digital signal processor (DSP), a special-purpose processor, and/or the like. 
         [0051]    The computer-readable storage media reader  612  can further be connected to a computer-readable storage media or medium  610 , together (and, optionally, in combination with storage device(s)  608 ) comprehensively representing remote, local, fixed, and/or removable storage devices plus storage media for temporarily and/or more permanently containing, storing, transmitting, and retrieving computer-readable information. The communications system  614  may permit data to be exchanged with the network and/or any other computer described above with respect to the system  600 . 
         [0052]    The computer system  600  may also comprise software elements, shown as being currently located within a working memory  618 , including an operating system  620  and/or other code  622 , such as an application program (which may be a client application, Web browser, mid-tier application, RDBMS, etc.). It should be appreciated that alternate embodiments of a computer system  600  may have numerous variations from that described above. For example, customized hardware might also be used and/or particular elements might be implemented in hardware, software (including portable software, such as applets), or both. Further, connection to other computing devices such as network input/output devices may be employed. 
         [0053]    Storage media and computer readable media for containing code, or portions of code, can include any appropriate media known or used in the art, including storage media and communication media, such as but not limited to volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage and/or transmission of information such as computer readable instructions, data structures, program modules, or other data, including RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, data signals, data transmissions, or any other medium which can be used to store or transmit the desired information and which can be accessed by the computer. Based on the disclosure and teachings provided herein, a person of ordinary skill in the art will appreciate other ways and/or methods to implement the various embodiments. 
         [0054]    The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the disclosure as set forth in the claims.
A reasonably-sized testing database instance can be efficiently replicated and maintained for a very large production database while retaining the characteristics and cross-sectional data. The performance characteristics are maintained in order to provide for proper testing of the production database for various application programs. Statistics on the type of data distribution for the customer data are obtained, allowing for parameters to be determined which can be used to store data only near the endpoints of the distribution (and/or at other key locations). In this way, a substantial amount of data skew is retained in a much smaller instance of the production database, allowing for easier performance testing, upgrade testing, etc.