Patent Publication Number: US-11023437-B2

Title: Data storage management based on indicated storage levels and other criteria for multi-level storage systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of and takes priority from the U.S. patent application Ser. No. 13/969,484, by John Mark Morris, entitled: “DATA STORAGE MANAGEMENT BASED ON INDICATED STORAGE LEVELS AND OTHER CRITERIA FOR MULTILEVEL STORAGE SYSTEMS,” filed on Aug. 16, 2013, which is hereby incorporated by reference herein in its entirety and for all purposes. 
     This application also takes priority from the U.S. Provisional Patent Application No. 61/747,593, entitled: “DATA STORAGE MANAGEMENT BASED ON INDICATED STORAGE LEVELS AND OTHER CRITERIA FOR MULTILEVEL STORAGE SYSTEMS,” filed on Dec. 31, 2012, which is hereby incorporated by reference herein in its entirety and for all purposes. 
    
    
     BACKGROUND 
     Data can be an abstract term. In the context of computing environments and systems, data can generally encompass all forms of information storable in a computer readable medium (e.g., memory, hard disk). Data, and in particular, one or more instances of data can also be referred to as data object(s). As is generally known in the art, a data object can, for example, be an actual instance of data, a class, a type, or a particular form of data, and so on. 
     Generally, one important aspect of computing and computing systems is storage of data. Today, there is an ever increasing need to manage storage of data in computing environments. Databases provide a very good example of a computing environment or system where the storage of data can be crucial. As such, to provide an example, databases are discussed below in greater detail. 
     The term database can also refer to a collection of data and/or data structures typically stored in a digital form. Data can be stored in a database for various reasons and to serve various entities or “users.” Generally, data stored in the database can be used by one or more the “database users.” A user of a database can, for example, be a person, a database administrator, a computer application designed to interact with a database, etc. A very simple database or database system can, for example, be provided on a Personal Computer (PC) by storing data (e.g., contact information) on a Hard Disk and executing a computer program that allows access to the data. The executable computer program can be referred to as a database program, or a database management program. The executable computer program can, for example, retrieve and display data (e.g., a list of names with their phone numbers) based on a request submitted by a person (e.g., show me the phone numbers of all my friends in Ohio). 
     Generally, database systems are much more complex than the example noted above. In addition, databases have been evolved over the years and are used in various business and organizations (e.g., banks, retail stores, governmental agencies, universities). Today, databases can be very complex. Some databases can support several users simultaneously and allow them to make very complex queries (e.g., give me the names of all customers under the age of thirty five (35) in Ohio that have bought all the items in a given list of items in the past month and also have bought a ticket for a baseball game and purchased a baseball hat in the past 10 years). 
     Typically, a Database Manager (DBM) or a Database Management System (DBMS) is provided for relatively large and/or complex databases. As known in the art, a DBMS can effectively manage the database or data stored in a database, and serve as an interface for the users of the database. For example, a DBMS can be provided as an executable computer program (or software) product as is also known in the art. 
     It should also be noted that a database can be organized in accordance with a Data Model. Some notable Data Models include a Relational Model, an Entity-relationship model, and an Object Model. The design and maintenance of a complex database can require highly specialized knowledge and skills by database application programmers, DBMS developers/programmers, database administrators (DBAs), etc. To assist in design and maintenance of a complex database, various tools can be provided, either as part of the DBMS or as free-standing (stand-alone) software products. These tools can include specialized Database languages (e.g., Data Description Languages, Data Manipulation Languages, Query Languages). Database languages can be specific to one data model or to one DBMS type. One widely supported language is Structured Query Language (SQL) developed, by in large, for Relational Model and can combine the roles of Data Description Language, Data Manipulation Language, and a Query Language. 
     Today, databases have become prevalent in virtually all aspects of business and personal life. Moreover, usage of various forms of databases is likely to continue to grow even more rapidly and widely across all aspects of commerce, social and personal activities. Generally, databases and DBMS that manage them can be very large and extremely complex partly in order to support an ever increasing need to store data and analyze data. Typically, larger databases are used by larger organizations, larger user communities, or device populations. Larger databases can be supported by relatively larger capacities, including computing capacity (e.g., processor and memory) to allow them to perform many tasks and/or complex tasks effectively at the same time (or in parallel). On the other hand, smaller databases systems are also available today and can be used by smaller organizations. In contrast to larger databases, smaller databases can operate with less capacity. 
     A current popular type of database is the relational database with a Relational Database Management System (RDBMS), which can include relational tables (also referred to as relations) made up of rows and columns (also referred to as tuples and attributes). In a relational database, each row represents an occurrence of an entity defined by a table, with an entity, for example, being a person, place, thing, or another object about which the table includes information. 
     One important objective of databases, and in particular a DBMS, is to optimize the performance of queries for access and manipulation of data stored in the database. Given a target environment, an “optimal” query plan can be selected as the best option by a database optimizer (or optimizer). Ideally, an optimal query plan is a plan with the lowest cost (e.g., lowest response time, lowest CPU and/or I/O processing cost, lowest network processing cost). The response time can be the amount of time it takes to complete the execution of a database operation, including a database request (e.g., a database query) in a given system. In this context, a “workload” can be a set of requests, which may include queries or utilities, such as, load that have some common characteristics, such as, for example, application, source of request, type of query, priority, response time goals, etc. 
     As noted above, one important aspect of computing environment is storage of data. Today, there is an ever increasing need to manage storage of data in computing environment, especially in database environment. 
     In view of the foregoing, techniques for storing data in computing systems and environments, especially database systems and environments are highly useful. 
     SUMMARY 
     Broadly speaking, the invention relates to computing environments and systems. More particularly, the invention relates to techniques for storing data in computing environments and systems, including database environments and systems. 
     In accordance with one aspect of the invention, data can be stored in a various Storage Levels of a multi-storage system, based on one or more indications and one or more other storage criteria. 
     The indications can effectively indicate or identify at least one storage level for storing at least one data object in a multi-storage system that includes multiple storages (e.g., storage devices) that are ranked or organized in accordance with various storage levels. By way of example, the indications can be provided as a user request or command that identifies a data object (e.g., a database table) and/or data associated with a command or operations (e.g., a particular database query) for storage in a particular storage level (e.g., Storage Level one (1) formed by one or more cache memory). In one embodiment, the indication can be provided as a “hot index” for a database. The “hot index” can, for example, be used as an optional index and used in a similar manner as other optional indexes in a database (e.g., as an index or a database table or a Join operation, or a transaction). 
     However, the indications, need not be the only basis for storing the data object in a multi-storage system. As noted above, one or more other storage criteria can also be considered in determining whether to store or continue to store the data object in a particular storage level that may be indicated by the indication. As a result, the indication can be used to effectively influence data storage but other storage criteria can be used as well to prevent adverse effects that can be caused by undue influence of indications. This can improve ensure and/or improve the overall efficiency of the system. It will be appreciated that the one or more other storage criteria considered in determining whether to store or continue to store the data object in a particular storage level can, for example, include the same criteria as used by the user (e.g., frequency of access) to serve as a verification mechanism, as well as other criteria that the users may not be aware of (e.g., current size of capacity of storage, relative importance of data even as may have been individually determined by the users themselves) to ensure and/or improve the overall efficiency of a computing system. 
     Also, it will be appreciated that the one or more other storage criteria (noted above) can be evaluated or revaluated on a continual basis in accordance with another aspect of the invention. As a result, storage assignments that were not or are no longer advisable can be effectively corrected by reassigning data to a Storage Level this is more appropriate as determined based on the one or more other storage criteria. This can also ensure and/or improve that the overall efficiency of a computing system is maintained or at least achieved some time after an unsound storage assignment has been made, rather than possibly honoring the assignment as a general rule and not reevaluating it. 
     Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1A  depicts a computing environment with a data storage management system in accordance with one embodiment of the invention. 
         FIG. 1B  depicts a method for managing storage of data in a multi-level storage in in accordance with one embodiment of the invention. 
         FIG. 2  depicts a data storage management system in a database environment in accordance with one embodiment of the invention. 
         FIG. 3  depicts a database node of a database system or a Database Management System (DBMS) in accordance with one embodiment of the invention. 
         FIG. 4  depicts a Parsing Engine (PE) in accordance with one embodiment of the invention. 
         FIG. 5  depicts a Parser in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     As noted in the background section, one important aspect of computing environment is storage of data. Today, there is an ever increasing need to manage storage of data in computing environment, especially in database environment. To this end, more recently, more sophisticated data management schemes have been introduced which aim to store or relocate data in a database based on frequency of access in order to further enhance performance. As such, data deemed to be accessed more frequently (“hot data”) may be stored or relocated, for example, from a hard disk to a Solid State Drive (SSD) or cache memory to facilitate faster access to data that is more frequently accessed in order to improve the overall performance of the system. 
     Generally, conventional techniques for storing data in computing systems and environments, especially database systems and environments are highly useful. However, conventional storage techniques may not provide the flexibility needed to balance the need or perceived needs of the users of the computing systems with the requirements for operating these systems in an efficient manner. For example, in a computing system, “hot data” can be stored in a storage device with a relatively faster access time, and other data (e.g., “cold data”) can be stored in storage device with a relatively slower access time. However, such a scheme may not fully address the needs of users that may, for example, want a particular database queries and/or set of data to be processed and/or made available as soon as possible. By way of example, it may be desirable to allow the database queries submitted by high ranking officer of a business organization to be executed as soon as possible despite the frequency of data access (i.e., how often such requests are submitted). 
     Hence, there is a need to provide a mechanism that allows selection of data, especially in a form that can be submitted by users, for storage in a particular form of storage (e.g., memory or SSDs with relatively faster access time than HHDs). However, allowing this type of selection, especially when user selection is the determinative factor or only factor can have serious drawback and negative effectives on a computing system. By way of example, a database user may inadvertently designate data (e.g., a database table) as “hot data” with the understanding that is would be used frequently, but, the data selected by the user is not actually used frequently and should not be treated as such. As another example, initially, data may be correctly designated as “hot data” by a database user but the data can later cease to be used as often as it had been before and should no longer be treated as “hot data.” Generally, it is not desirable to put users, especially end-users, in charge of specific data storage management and maintenance, yet there is a need to give them some control over such activities. 
     In view of the foregoing, improved techniques for storing data in a computing environments and systems, especially database environments and systems are needed and would be very useful. 
     Accordingly, improved techniques for storing data in a computing environments and systems, including database environments and system are disclosed. 
     More specifically, it will be appreciated that data can be stored in a various Storage Levels of a multi-storage system, based on one or more indications and one or more other storage criteria, in accordance with one aspect of the invention. 
     The indications can effectively indicate or identify at least one storage level for storing at least one data object in a multi-storage system that includes multiple storages that are ranked or organized in various storage levels. By way of example, the indications can be provided as a user request or command that identifies a data object (e.g., a database table) and/or data associated with a command or operations (e.g., a particular database query) for storage in a particular storage level (e.g., Storage Level one (1) formed by one or more cache memory). In one embodiment, the indication can be provided as a “hot index” for a database. The “hot index” can, for example, be used as an optional index and used in a similar manner as other optional indexes in a database (e.g., as an index or a database table or a Join operation, or a transaction). 
     The indication, however, need not be the only basis for storing the data object in a multi-storage system. As noted above, one or more other storage criteria can also be considered in determining whether to store or continue to store the data object in a particular storage level that may be indicated by the indication. As a result, the indication can be used to effectively influence data storage but other storage criteria can be used as well to prevent adverse effects caused by undue influence and to ensure the overall efficiency of the system. It will be appreciated that the one or more other storage criteria considered in determining whether to store or continue to store the data object in a particular storage level can include the same criteria as used by the user (e.g., frequency of access) to serve as a verification mechanism, as well as other criteria that the users may not be aware of (e.g., current size of capacity of storage, relative importance of data even as may have been individually determined by the users themselves) to ensure the overall efficiency of a computing system. 
     Also, it will be appreciated that the one or more other storage criteria can be evaluated or revaluated on a continual basis in accordance with another aspect of the invention. As a result, storage assignments that were not or are no longer advisable can be effectively corrected by reassigning data to a Storage Level this is more appropriate as determined by the one or more other storage criteria. This can also ensure that the overall efficiency of a computing system is maintained or at least achieved some time after an unsound storage assignment may have been made and possibly honored as a general rule. 
     Embodiments of these aspects of the invention are also discussed below with reference to  FIGS. 1A-5 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments. 
       FIG. 1A  depicts a computing environment  100  with a data storage management (DSMS) system  101  in accordance with one embodiment of the invention. Referring to  FIG. 1A , the DSMS  101  can effectively facilitate and/or manage storage of data  104  in the computing environment  100 . 
     More particularly, DSMS  101  can manage storage of data  104  in multiple storages (e.g., storage devices, portions of a storage device) S 1 -SN that are respectively associated with multiple storage levels SL 1 -SLN that can be ordered based on or more storage ordering criteria (e.g., relative access speed, relative storage capacity, relative reliability). The multiple storage S 1 -SN can form or be a multi-storage data system or device. The storage levels SL 1 -SLN can represent multiple conceptual levels defined based on one or more storage ordering criteria for arranging multiple storages SL 1 -SLN. It should be that more than one (1) storage S can be in the same storage level SLi. In other words, referring to  FIG. 1A , a storage Si can represent multiple storage portions or multiple storage devices. By way of example, one or more memory-based storages (e.g., cache, RAM memory, processors cache) can be in one Storage Level, and one or more storages that are based on Solid State Drive (SSD) can be in another Storage Level, and so on. As suggested by  FIG. 1A , the storages S 1 -SN can, for example, be part of a computing device and/or computing system  102 . 
     In any case, it will be appreciated that the DSMS  101  can manage storage of the data  104  in multiple storages S 1 -SN based on at least one indication  106  and one or more other storage criteria  108 . Generally, the indication(s)  106  can be indicative of at least one storage level for storing at least one data object in the storages 1-N or a multi-storage system or device that they can represent. BY way of example, the indication(s)  106  can be provided and obtained by the DSMS  101  as user input that is indicative of a desire to store a particular data object A and/or one or more data objects associated with a command, user, priority, etc. in a particular Storage Level (SLi). For example, in the context of a database, a database command or request can be provided that is indicative of a user desire to store data associated with a table and/or a query from a particular user or of a particular priority in a high-level access storage (e.g., memory). As such, the DSMS  101  can facilitate storage of the data  104  in a Storage Level indicated by the indication(s)  106 . 
     Moreover, it will be appreciated that in addition to the indication(s)  106 , DSMS  101  can also consider one or more other storage criteria  108 . In other words, in managing and facilitating storage of the of the data  104 , the DSMS  101  need not be limited to the indication(s)  106  and can consider one or more other storage criteria  108 . It will be appreciated that one or more other storage criteria  108  can be virtually anything, including, for example, assessed, estimated and/or actual frequency of usage, including physical and virtual access of data, limit of storage or space availability in a particular storage level, initial or perceived priority associated with data, current or actual assessed priorities that may differ from initial or perceived priorities, “hotness” of data defined based one or more criteria, including, for example, frequency of data and determined priority, and comparative measures for comparing data with respect to other data. 
     In any case, the DSMS  101  can effectively use the one or more other storage criteria  108  to determine whether to store and/or to continue to store the data object  104  in a Storage Level Si as indicated by the indication(s)  106 . In other words, the DSMS  101  can store data  104  as indicated by the indication(s)  106  but can also effectively test the soundness of storing data  104  in the manner indicated by the indication(s)  106  based on one more or more other storage criteria  108 . Although, generally, the one or more storage criteria  108  can be system defined, user defined and any combination thereof, it will be appreciated that at least one storage criteria  108  can be defined by a system administrator and used to test the soundness of indication(s)  106  that may be provided by user(s). 
     Moreover, the DSMS  101  can effectively monitor storage of the data  104  to determine based on the one or more storage criteria  108  whether to allow the storage of the data  104  to continue as may have been indicated by the indication(s)  106 . As such, although DSMS  101  could allow data  104  to be stored as indicated by the indication(s)  106 , it can later determine not to allow data  104  to be stored in the Storage Level indicated by the indication(s)  106 . 
     It should be noted that determining of whether to store or continue to store the data  104  in a Storage Level SLi indicated by the indication(s)  106 , based on one or more storage criteria  108 , can also be made based on monitoring performed by the DSMS  101  or another component (not shown). By way of example, one or more storage attributes associated with a data object can be monitored to determine one or more storage rating values for the data object. In the example, one or more storage attributes (e.g., data “hotness,” data “priorities”) can be defined and monitored for one or more selected data objects or across a system to achieve a storage rating system for data. As an example, the number of times data in a storage portion (e.g., a cylinder on a storage drive) is accessed can be counted and/or data associated with a high priority database request can be assigned a high priority in order to obtain storage ratings for virtually all of data stored in a system. 
     At any rate, the DSMS  101  can be configured to monitor storage one or more attributes associated with the one or more storage criteria  108  to obtain storage monitoring data  108  and/or can be configured to merely obtain the storage monitoring data  108  as data monitored and provide by another component (e.g., a system storage monitor, a database regulator). The storage monitoring data  108  can allow the DSMS  101  to effectively evaluate the one or more storage criteria  108  in order to determine whether to allow storage or continue to allow storage of the data  104  in a Storage Level Si as indicated by the indicator(s)  106 . By way of example, data “hotness” rating can be determined based on frequency of access (physical as well as virtual access) as well as other factors, including, for example, priority associated with the data. In addition, other criteria, including, for example, amount of space currently available in a given Storage Level Si, relative “hotness” rating of data can be compared with other data, for example, also requested to be stored or already stored in the given Storage Level (Si) can be considered by the storage evaluation component  204  in determining whether to allow storage or continue to allow storage of data in the Storage Level Si as indicated or requested by the indication or request  210 . In effect, this evaluation or monitoring can be done on a continual basis to avoid or counter harmful effects of the storage priorities and assignments that may made been made by user while still allowing the users of databases to make such requests or assignments for storage of data as they may see fit. As such, the evaluation or monitoring can provide a safety mechanism that depending on the desired configuration may deny requests for storage of data in a particular storage level SLi if one or more determined criteria is not met, or allow them initially and later effectively cancel the assignment of data to a particular storage level SLi when it is determined that one or more determined criteria are not met or are no longer met. Hence, user requests can be effectively balanced with a system of check and balances that can be performed on a continual basis to ensure the system will be well balanced. 
     Although depicted as a separate component in  FIG. 1A , those skilled in the art will readily appreciate that the DSMS  101  can be part of the computing device  110 . Those skilled in the art will also readily appreciate that the DSMS  101  can be provided as one or more hardware and/or software components, for example, at least in part as computer executable code stored in a computer readable storage medium (not shown) and executed by one or more processors (not shown). 
       FIG. 1B  depicts a method  150  for managing storage of data in a multi-level storage in in accordance with one embodiment of the invention. The multiple storages can be part of a multi-storage system. More particularly, the multiple storages can be respectively associated with multiple storage levels in an arrangement such that each one of the storage levels includes one or more storages of the multiple storages of multi-storage system. 
     Referring to  FIG. 1B , initially, at least one indication is obtained ( 152 ) The indication can be indicative of at least one storage level for storing at least one data object in the multi-storage system. Next, the indication can effectively be evaluated ( 154 ) based on one or more storage criteria. Accordingly, it can be determined ( 156 ) based on one or more storage criteria whether to allow (or continue to allow) the at least one data object to be stored in at least one storage of the at least one storage level as indicated by the at least one indication. Thereafter, the at least one data object can be allowed ( 158 ) to be stored (or continued to be stored) in the at least one storage level indicated by the at least one indication if it is determined ( 156 ) to do so. Thereafter, the method  150  can continue to evaluate or reevaluate the decision ( 160 ) made to allow or effectively deny storage of the at least one data object in the at least one storage of the at least one storage level, as indicated by the at least one indication, until it is determined ( 158 ) to end the method  150 , for example, as a result of system shutdown. 
     Referring back to  FIG. 1A , the DSMS  101  is especially useful for a database environment. As such, a DSMS provided in a database environment will be discussed in greater detail. To further elaborate,  FIG. 2  depicts a DSMS  201  in a database environment  200  in accordance with one embodiment of the invention. As suggested by  FIG. 2 , DSMS  201  can, for example, be part of a DBMS provided in the database environment  200 . 
     Referring to  FIG. 2 , conceptually, the DSMS  201  can include multiple components, including an storage request component  202 , and storage evaluation component  204 , and a manager (or a main) component  206 , as well other optional components, such as, storage monitoring  208 . This storage request component  202  can effectively serve as an interface for processing indications  210  indicative of a storage level for storing a data object. In a database environment, the indications  210  can be received as a database request and/or command  210  provided by a database user. By way of example, a “hot index” can be provided as an option similar to other optional indexing mechanisms that are provided in database environments. As such, in the example, a “hot index” can, for example, can be provided as an indexing mechanism that can be used on tables, partitions and/or transactions of the database, as well as an indexing mechanism that can be used for various database requests, commands and constructs (e.g., hot index on or as a join index). 
     In any case, the storage request component  202  can receive, as input, indications or requests  210 , for storing data in a particular data storage level LS 1 -SLN. In the example, a data storage level L 1 -LN can represent a number of storages or types of storages locally organized. BY way of example, SL 1  can represent cache memory available (e.g., FSG cache for caching hot data), SL 2  can present fast-access storage available for storing hot data (e.g., SSD storage for storing hot data), and SL 3  can be slow-access storage (e.g., disk drives with relatively larger capacity for storing data that is not hot). 
     The storage evaluation component  204 , can effectively evaluate Indications or requests  210  in order to determine whether to allow storage of the data into the particular data storage level indicated or requested. This evaluation can be performed by the storage evaluation component  204  based on one or more storage criteria  220  as well as monitoring data  224 . The monitoring data  224  can reflect the information gathered based on one or more storage attributes associated with the one or more storage criteria  220 . 
     As suggested by  FIG. 2 , the monitoring data  224  can be effectively collected at least in part by a storage monitoring component  208 . Alternatively, or in addition to the monitoring that can be performed by the monitoring component  208 , monitoring data  224  can be provided by one or more other components in the database environment  200 , such as, for example a database Optimizer, a database monitor or regulator, etc. the manager component  206  can effectively manage the activities of the other components and/or facilitate communication between them in order to determine whether to store or continue to store the data object in a storage level SLi as indicated by the indication or request  210 . 
     Additional information regarding a database regulator that can be provide information relating to storage usage of data in order to assist in making decision regarding assignment of data to a particular storage or storage level is, for example, described in the U.S. Pat. No. 7,702,676, entitled: “PARALLEL VIRTUAL OPTIMIZATION,” by Brown et al., which is hereby incorporated by reference herein, in its entirety with all the material it may incorporate by reference and for all purposes. 
     Additional information regarding techniques for considering priority of data in the form of priority of database workloads in assessing data “temperature” or “hotness” are described in the U.S. patent application Ser. No. 11/716,880 entitled: “workload priority influenced data temperature, by Morris et al., which is hereby incorporated by reference herein, in its entirety with all the material it incorporates by reference, and for all purposes. 
     It will be appreciated that the data storage management system DSMS  201  (shown in  FIG. 2 ) is especially suitable for large database systems with a large number of storage device, including large parallel or multiprocessing database systems that may be comprised of multiple database nodes (or nodes) that each can have their own storage devices and processors. As such, the data DSMS  201  is described further in the context of a parallel or multiprocessing database system. 
     To further elaborate,  FIG. 3  depicts a database node  1105  of a database system or a Database Management System (DBMS)  1000  in accordance with one embodiment of the invention. The DBMS  1000  can, for example, be provided as a Teradata Active Data Warehousing System. It should be noted that  FIG. 3  depicts in greater detail an exemplary architecture for one database node  1105   1  of the DBMS  1000  in accordance with one embodiment of the invention. 
     Referring to  FIG. 3 , the DBMS node  1105   1  includes multiple processing units (or processing modules)  1110 -N connected by a network  1115 , that manage the storage and retrieval of data in data-storage facilities  1120   1-N . Each of the processing units  1110 -N can represent one or more physical processors or virtual processors, with one or more virtual processors (e.g., an Access Module Processer (AMP)) running on one or more physical processors in a Teradata Active Data Warehousing System). For example, when provided as AMPs, each AMP can receive work steps from a parsing engine (PE)  1130  which is also described below. 
     In the case in which one or more virtual processors are running on a single physical processor, the single physical processor swaps between the set of N virtual processors. For the case in which N virtual processors are running on an M-processor node, the node&#39;s operating system can schedule the N virtual processors to run on its set of M physical processors. By way of example, if there are four (4) virtual processors and four (4) physical processors, then typically each virtual processor could run on its own physical processor. As such, assuming there are eight (8) virtual processors and four (4) physical processors, the operating system could schedule the eight (8) virtual processors against the four (4) physical processors, in which case swapping of the virtual processors could occur. 
     In the database system  1000 , each of the processing units  1110   1-N  can manage a portion of a database stored in a corresponding one of the data-storage facilities  1120   1-N . Also, each of the data-storage facilities  1120   1-N  can include one or more storage devices (e.g., disk drives). Again, it should be noted that the DBMS  1000  may include additional database nodes  1105   2-O  in addition to the database node  1105   1 . The additional database nodes  1105   2-O  can be connected by extending the network  1115 . Data can be stored in one or more tables in the data-storage facilities  1120   1-N . The rows  1125   1-Z  of the tables can, for example, be stored across multiple data-storage facilities  1120   1-N  to ensure that workload is distributed evenly across the processing units  1110   1-N . In addition, a parsing engine  1130  can organize the storage of data and the distribution of table rows  1125   1-Z  among the processing units  1110   1-N . The parsing engine  1130  can also coordinate the retrieval of data from the data-storage facilities  1120   1-N  in response to queries received, for example, from a user. The DBMS  1000  usually receives queries and commands to build tables in a standard format, such as, for example, SQL. Parsing engine  1130  can also handle logons, as well as parsing the SQL requests from users, turning them into a series of work steps that can be sent to be executed by the processing units  1110   1-N . 
     For example, a client-side Host  1004  (e.g., a Personal Computer (PC), a server) can be used to logon to the database system  1000  provided as a Teradata DBS server. Commination between the client-side Host  1004  and the database system  1000  can be facilitated by a database communicating mechanism, for example, by an ANSI CLI (Call Level Interface) standard that can include parcel requests and responses that facilitate the movement of files resident on the client-side host  1004  over to the database system  1000 . 
     For example, the rows  1125   1-Z  can be distributed across the data-storage facilities  1120   1-N  by the parsing engine  1130  in accordance with their primary index. The primary index defines the columns of the rows that are used for calculating a hash value. The function that produces the hash value from the values in the columns specified by the primary index may be called the hash function. Some portion, possibly the entirety, of the hash value can be designated a “hash bucket”. As such, the hash buckets can be assigned to data-storage facilities  1120   1-N  and associated processing units  1110   1-N  by a hash bucket map. The characteristics of the columns chosen for the primary index, determine how evenly the rows are distributed. 
     Referring again to  FIG. 3 , it should be noted that a data storage management system (DSMS)  1002  can be provided as a central component for the processing units  1110   1-N . However, it should be noted that each one of the processing units  1110   1-N  can be effectively provided with a local data management system (not shown) that can serve as a local component and possibly collaborate with the central data management system  1002 . Of course, various other configurations are possible and will become readily apparent in view of the foregoing. 
     Referring now to  FIG. 4 , in one exemplary system, the parsing engine  1130  can be made up of three components: a session control  1200 , a parser  1205 , and a dispatcher  1210 . In the example, the session control  1200  provides the logon and logoff function. It accepts a request for authorization to access the database, verifies it, and then either allows or disallows the access. When the session control  1200  allows a session to begin, a user may submit a SQL request, which is routed to the parser  1205 . Regarding the dispatcher  1210 , it should be noted that some monitoring functionality for data management and/or workload management may be performed by a regulator to monitor workloads and usage of the resources, for example, by using internal messages sent from the AMPs to the dispatcher  1210 . The dispatcher  1210  can provide an internal status of every session and request running on the system, for example, by using internal messages sent from the AMPs to the dispatcher  1210 . In the example, the dispatcher  1210  can provides an internal status of every session and request running on the system. As such, at least part of a database management ( 1250 ) can be provided by the dispatcher  1210  in accordance with one embodiment of the invention. The dispatcher  1210  can also operate as a workload dispatcher in order to effectively manage workloads, as well as storage of data, including storage of data in a particular Storage Level SLi in accordance with the techniques disclosed above. As such, at least part of data management system ( 1250 ) can be provided by the dispatcher  1210  in accordance with one embodiment of the invention 
     As illustrated in  FIG. 5 , the parser  1205  interprets the SQL request  1300 , checks it for proper SQL syntax  1305 , evaluates it semantically  1310 , and consults a data dictionary to ensure that all of the objects specified in the SQL request actually exist and that the user has the authority to perform the request  1305 . Finally, the parser  1205  runs an optimizer  1320 , which can generate the least expensive plan to perform the request. It will be appreciated that the optimizer  1320  can also be configured to take part in assignment of data to a particular Storage Level (SLi) in accordance with the techniques disclosed above. As such, at least part of data management system ( 1250 ) can be provided by the optimizer  3120  in accordance with one embodiment of the invention. 
     Generally, various aspects, features, embodiments or implementations of the invention described above can be used alone or in various combinations. Furthermore, implementations of the subject matter and the functional operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Implementations of the subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter affecting a machine-readable propagated signal, or a combination of one or more of them. The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus. 
     A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, subprograms, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network. 
     The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). 
     Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. However, a computer need not have such devices. Moreover, a computer can be embedded in another device, e.g., a mobile telephone, a personal digital assistant (PDA), a mobile audio player, a Global Positioning System (GPS) receiver, to name just a few. Computer readable media suitable for storing computer program instructions and data include all forms of nonvolatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CDROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry. 
     To provide for interaction with a user, implementations of the subject matter described in this specification can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, tactile or near-tactile input. 
     Implementations of the subject matter described in this specification can be implemented in a computing system that includes a backend component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a frontend component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the subject matter described is this specification, or any combination of one or more such backend, middleware, or frontend components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (“LAN”) and a wide area network (“WAN”), e.g., the Internet. 
     The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. 
     While this specification contains many specifics, these should not be construed as limitations on the scope of the disclosure or of what may be claimed, but rather as descriptions of features specific to particular implementations of the disclosure. Certain features that are described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
     The various aspects, features, embodiments or implementations of the invention described above can be used alone or in various combinations. The many features and advantages of the present invention are apparent from the written description and, thus, it is intended by the appended claims to cover all such features and advantages of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, the invention should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention.