Patent Publication Number: US-2023161672-A1

Title: Archive control techniques for database systems

Description:
BACKGROUND 
     Technical Field 
     This disclosure relates generally to database systems and more specifically to controlling archive operations to mitigate storage space issues. 
     Description of the Related Art 
     Database systems may store large data sets and the integrity of data may be important. Therefore, database systems typically perform various archive operations to generate backup versions of database information. This may include full backups of a database, partial backups, and database log backups, for example. 
     Availability of a database is also an important consideration for database system design. In some scenarios, archival activity can cause issues with storage space, which may affect the ability of the database system to remain available. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a flow diagram illustrating an example method for pausing and resuming archiving, according to some embodiments. 
         FIG.  2    is a block diagram illustrating a detailed example database system configured to perform archive operations for multiple database cells, according to some embodiments. 
         FIG.  3    is a state diagram illustrating detailed example states for an archival circuit breaker, according to some embodiments. 
         FIG.  4    is a flow diagram illustrating another example method, according to some embodiments. 
         FIG.  5    is a block diagram illustrating elements of a multi-tenant system, according to some embodiments. 
         FIG.  6    is a block diagram illustrating elements of a computer system configured to implement various systems described in the present disclosure, according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     As discussed above, archive operations for a database system may occasionally cause storage space concerns (e.g., due to lack of available disc space when archive operations generate extra files for archiving). As one example context, some relational databases use log-structured merge-trees (LSM trees) as underlying storage. U.S. patent application Ser. No. 15/884,131, filed Jan. 30, 2018, is incorporated by reference herein in its entirety and discusses example record lookup techniques in the LSM data structure context. In LSM tree implementations, data is typically first written to a memory component and later transferred to on-disc storage, where it is merged through levels of a data structure. Each node in the data structure may correspond to a file (also referred to as an extent) that is used to store records. This may allow writing to the root level of the disc storage rather than locating and overwriting previous version(s) of the data. LSM tree implementations may also generate log files that track database operations, e.g., for purposes of system recovery. 
     In the LSM tree context, archive activity (both for log data and LSM node extents) may use substantial disc space. For example, the database system may copy extents to capture a snapshot of the extents at a given time (given that extents of the LSM tree may be subsequently updated by database activity before the backup completes) and schedule the copied extents for storage. In some scenarios, this may use unusual amounts of disc space. For example, when there is an aborted ticket for log archival or backup slowness the archival system may hold off too many extents and eventually crash the database. 
     In disclosed embodiments discussed in detail below, the database system is configured to pause and cancel archive operations in certain scenarios. This may trade point-in-time recoverability for database availability. The pause/cancel implementation may be analogized to an archival “circuit breaker” that trips enter a non-default archive state in which archive activity is paused, based on various metrics such as available storage space, the characteristics of extents in-flight for archiving, etc. 
     Thus, the disclosure below is directed to the technical field of database systems and more particularly to archive activity and increasing database availability. Disclosed embodiments address the technical problem of disc space issues related to archive activity which could cause database unavailability. The disclosed technical solutions track various database parameters over time and pause archive activity in certain scenarios to avoid running out of disc space, thereby advantageously improving database availability relative to traditional techniques. 
     Overview of Archival Circuit Breaker Embodiments 
       FIG.  1   . is a flow diagram illustrating example archive state transitions, according to some embodiments. In the illustrated embodiment, the system operates in a default archive operation state at  110 . In this state, the system may perform periodic backups, on-demand backups, backups of log files, etc. Speaking generally, various known or future techniques may be used to store backups in this state. In the LSM-tree context, backups may involve duplicating extents and scheduling them for backup to disc storage. 
     At  120 , in the illustrated embodiment, the system determines whether one or more storage space related thresholds are met. For example, the system may determine whether in-flight archive extents meet a threshold data size (where “in-flight” refers to extents for which storage of which has been initiated, but not yet completed), other characteristics of the log extents in-flight, etc. As another example, the system may determine whether a threshold amount of disc storage is available. In some embodiments, the system may logically combine multiple parameters to determine whether one or more thresholds are met for tripping the circuit breaker. If the threshold(s) are met, flow proceeds to  130 . If not, flow proceeds back to  110  and the system remains in the default state. 
     At  130 , in the illustrated embodiment, the system pauses archiving and cancels one or more pending archive operations (this may include deleting one or more extents scheduled for disc storage). The system remains in the pause state for archiving until one or more archive-resume conditions are met, as determined at  140 . One the resume condition(s) are met, flow proceeds to  110  and the system re-enters the default state (the circuit-breaker is closed). For example, the system may wait a threshold time interval, check for a threshold disc space availability before re-entering the default state, or both. In some embodiments, the system may logically combine multiple parameters to determine whether one or more conditions are met for closing the circuit breaker. 
     In some embodiments, there may be one or more transition states between the yes result at  140  and arriving back at  110 , e.g., to perform a full backup, check storage metrics, etc. before resuming default operation. Example transition states are discussed below with reference to  FIG.  3   . Note that the illustrated operations may be performed on a per-cell (e.g., per-database) granularity such that some databases may continue archive activity while others are paused. Further, different cells may have different thresholds for tripping/closing the archival circuit breaker. 
     Example Database System with Archival Circuit Breaker 
       FIG.  2    is a block diagram illustrating a detailed example database system that may implement disclosed archive techniques, according to some embodiments. In the illustrated embodiment, the system includes Salesforce Application Model (SAM) cluster  210 , relational database service (RDS)  220 , production cluster  230 , restore cluster  240 , and storage service  250 . Note that various elements of  FIG.  2    may be maintained at different locations and connected via various appropriate types of networks. Note that the example of  FIG.  2    is included for purposes of illustration to explain one example Salesforce implementation, but this figure is not intended to limit the scope of the present disclosure; various database system architectures are contemplated. 
     SAM cluster  210 , in the illustrated embodiment, maintains a plurality of cells A through N. In the illustrated example, SAM cluster  210  includes a core application instance  212  for each cell. SAM cluster  210  also implements an archive service  214 , which communicates with RDS  220  and proxy service  216 . Proxy service  216  may provide a transparent data access layer that intelligently routes queries to the most optimal data source, resulting in SQL offload and improved response times. For example, proxy service  216  may cache SQL results and track SQL queries so they are routed to the appropriate database node for fresh data. RDS  220  provides relational database functionality. The archive service  214  may store metrics using proxy service  216  and may store scheduling and archival metadata in RDS  220 . 
     Production cluster  230 , in the illustrated embodiment, includes salesforce database (SDB) store  237  (which may be implemented by book-keeper storage servers), archive copy workers  238 , and the following for each cell: a log archive agent  232 , an SDB (which may be implemented by a database management server)  234 , and an archive agent  236 . In some embodiments, log archive agent  232 , archive agent  236 , or both implement disclosed archival circuit breaker techniques. As shown, the log archive agent  232  and archive agent  236  coordinate with archive service  214  and communicate with the SDB  234  and determine extents that should be archived. The archival copy workers  238  then copy/backup data from SDB store  237  for the production cluster to storage service  250  (and one or more archival copy workers  248  may similarly copy/restore data into the SDB store  246  in the restore cluster  240  based on configuration by restore agent  244 ). Storage service  250  may be S 3  storage, for example. 
     The system may utilize various metadata and metrics discussed with reference to  FIG.  2    to determine when to open and close the archival circuit breaker, among other types of information. For example, the system may trigger opening/closing based on triggers associated with metrics stored via proxy service  216 , scheduling and archival metadata stored in RDS  220 , log data, information shared between archival modules, etc. 
     Production cluster  230  and restore cluster  240  may also implement respective metadata servers, which are not shown in  FIG.  2   . In various embodiments, implementing disclosed archival circuit breaker techniques for an archive agent of a cell may advantageously increase availability of the cell, relative to traditional techniques. 
     In some embodiments, the circuit breaker techniques may use different thresholds for different cells. For example, some cells may have higher data retention priority than others. These cells may wait longer to trip their circuit breaker, e.g., to maintain more point-in-time backup data. Therefore, the system may use different thresholds for amounts of extents in-flight, disc space available, time intervals, etc. for different cells. 
     Further, the system may dynamically adjust various thresholds based on historical data. For example, the system may store various operational state information at different points in time. This may include the amount of extents in-flight for backup (e.g., the amount of disc space needed by in-flight extents, the number of in-flight extents, etc.), disc space availability, operation conditions specifically associated with unavailability of the database due to lack of disc space, etc. The system may implement various logic to determine when to adjust a threshold. For example, the system may use one or more machine learning models to adjust one or more thresholds. For example, a machine learning module may implement a model using any of various appropriate topologies, such as, without limitation: neural network, naïve Bayes, decision tree, linear regression, learning vector quantization, random forest, K-nearest neighbors, etc. The model may adjust thresholds to attempt to provide good point-in-time archive characteristics while avoiding database unavailability due to running out of disc space. 
     In some embodiments, some cells may not implement archival circuit breaker techniques at all. Further, the granularity at which backups may be paused/resumed may vary in different embodiments. For example, while the examples discussed above include one or more agents with archival circuit breaker features per cell, this functionality may be implemented at the granularity of an entire SAM cluster instead, for example, or for one or more sub-portions of a cell. 
     More Detailed State Diagram 
       FIG.  3    is a more detailed state diagram for an archival circuit breaker, according to some embodiments. In the illustrated embodiment, the system remains in the closed state  310  for default archival operation until there is a threshold amount of log extents in flight at  315 . This threshold may be measured in terms of the sum of the sizes of in-flight extents, for example. In other embodiments, this threshold may be determined as an estimate, e.g., based on the number of in-flight extents and a predicted greatest-possible extent size. In some embodiments, element  315  also checks whether there is a threshold amount of disc space available. As discussed above with reference to  FIG.  1   , element  315  may consider multiple parameters in conjunction to determine whether to trip the archival circuit breaker. If the threshold is met, flow proceeds to  320 . 
     At  320 , in the illustrated embodiment, the system deletes the backup log window (the list of extents to be backed up). This may allow the system to delete extents from primary storage to free up disc space. At  325 , in the illustrated embodiment, the system is in the circuit-breaker-open state and archive operations for the database are paused. 
     At  330 , the systems determines whether it should try to close the circuit breaker. This may include waiting for a threshold time interval, checking for a threshold amount of disc space available, etc., or some combination thereof. If element  330  determines a positive result, the system transitions to half-open state  335 . In this state, the system checks whether a backup log window exists at  340  and triggers a full backup if so (which will create a backup log window). The system waits at  350  until the full backup has successfully completed and then transitions back to closed state  310 . If the backup fails at  350 , the system deletes the backup log window and transitions back to the open state. 
     Example Method 
       FIG.  4    is a flow diagram illustrating an example method, according to some embodiments. The method shown in  FIG.  4    may be used in conjunction with any of the computer circuitry, systems, devices, elements, or components disclosed herein, among others. In various embodiments, some of the method elements shown may be performed concurrently, in a different order than shown, or may be omitted. Additional method elements may also be performed as desired. 
     At  410 , in the illustrated embodiment, a database system initiates one or more archive operations to archive one or more data extents for a database maintained by the database system. In some embodiments, the database is maintained by the database system using a log-structured merge-tree (LSM tree) and the data extents are elements of the LSM tree that are duplicated by the database system when generating an archive snapshot of the database. 
     At  420 , in the illustrated embodiment, a database system halts archive activity for the database, in response to determining that archive operations for a threshold amount of data extents are initiated but not completed. The halting may be further based on determining that less than a threshold amount of storage space is available. The amount of data extents may indicate to the data size of in-flight data extents, number of in-flight data extents, other characteristics of in-flight data extents, or some combination thereof. 
     At  430 , in the illustrated embodiment, a database system cancels at least one of the one or more archive operations. The database system may also delete one or more duplicate extents that were generated for one or more canceled archive operations. More generally, the database system may delete backup files, metadata, etc. that is not used while archiving is paused. The system may further delete a backup log window. The system may, in response to a threshold time interval elapsing, transitioning to a half-open operating state. The system may trigger a full backup of the database in the half-open operating state. The system may, in response to successful completion of the full backup, transition to a default operating state. The transition to the half-open state is may be further based on a determination that a threshold amount of storage space is available. 
     At  440 , in the illustrated embodiment, a database system determines to resume archive activity for the database based on determinations that (A) a threshold timer interval has elapsed and (B) a threshold amount of storage space is available for the database system. In other embodiments, the database system may determine to resume archive activity based on only one of these determinations or on some combinations of one or more of these determinations with one or more other parameters. 
     In some embodiments, the database system stores different halt thresholds for different databases maintained by the database system. The database system may halt archive activity for a second database in response to determining that archive operations for a different threshold amount of data extents are initiated but not completed. The database system may cancel one or more archive operations for the second database. This may advantageously allow customization of archival circuit-breaker functionality for different cells with different data retention priorities, for example. 
     In some embodiments, the database system stores historical data that indicates database status information for one or more prior archive halt operations (e.g., amounts of in-flight extents at different times, operating state associated with unavailability of a database, database characteristics at different times, etc.). The system may dynamically adjust one or more thresholds for halting or resuming archive operations for the database based on the historical data. For example, the system may adjust a threshold amount of data extents in flight, a threshold disc space available, a threshold time interval, etc. In some embodiments, a machine learning module performs the dynamic adjustment. 
     Example Multi-Tenant Database System 
     Turning now to  FIG.  5   , an exemplary multi-tenant database system (MTS)  500  in which various techniques of the present disclosure can be implemented is shown. In  FIG.  5   , MTS  500  includes a database platform  510 , an application platform  520 , and a network interface  530  connected to a network  540 . Also as shown, database platform  510  includes a data storage  512  and a set of database servers  514 A-N that interact with data storage  512 , and application platform  520  includes a set of application servers  522 A-N having respective environments  524 . In the illustrated embodiment, MTS  500  is connected to various user systems  550 A-N through network  540 . The disclosed multi-tenant system is included for illustrative purposes and is not intended to limit the scope of the present disclosure. In other embodiments, techniques of this disclosure are implemented in non-multi-tenant environments such as client/server environments, cloud computing environments, clustered computers, etc. 
     MTS  500 , in various embodiments, is a set of computer systems that together provide various services to users (alternatively referred to as “tenants”) that interact with MTS  500 . In some embodiments, MTS  500  implements a customer relationship management (CRM) system that provides mechanism for tenants (e.g., companies, government bodies, etc.) to manage their relationships and interactions with customers and potential customers. For example, MTS  500  might enable tenants to store customer contact information (e.g., a customer&#39;s website, email address, telephone number, and social media data), identify opportunities, record service issues, and manage marketing campaigns. MTS  500  may also enable those tenants to identify how customers have been communicated with, what the customers have bought, when the customers last purchased items, and what the customers paid. To provide the services of a CRM system and/or other services, as shown, MTS  500  includes a database platform  510  and an application platform  520 . 
     Database platform  510 , in various embodiments, is a combination of hardware elements and software routines that implement database services for storing and managing data of MTS  500 , including tenant data. As shown, database platform  510  includes data storage  512 . Data storage  512 , in various embodiments, includes a set of storage devices (e.g., solid state drives, hard disk drives, etc.) that are connected together on a network (e.g., a storage attached network (SAN)) and configured to redundantly store data to prevent data loss. In various embodiments, data storage  512  is used to implement a database comprising a collection of information that is organized in a way that allows for access, storage, and manipulation of the information. Data storage  512  may implement a single database, a distributed database, a collection of distributed databases, a database with redundant online or offline backups or other redundancies, etc. As part of implementing the database, data storage  512  may store files that include one or more database records having respective data payloads (e.g., values for fields of a database table) and metadata (e.g., a key value, timestamp, table identifier of the table associated with the record, tenant identifier of the tenant associated with the record, etc.). 
     In various embodiments, a database record may correspond to a row of a table. A table generally contains one or more data categories that are logically arranged as columns or fields in a viewable schema. Accordingly, each record of a table may contain an instance of data for each category defined by the fields. For example, a database may include a table that describes a customer with fields for basic contact information such as name, address, phone number, fax number, etc. A record therefore for that table may include a value for each of the fields (e.g., a name for the name field) in the table. Another table might describe a purchase order, including fields for information such as customer, product, sale price, date, etc. In various embodiments, standard entity tables are provided for use by all tenants, such as tables for account, contact, lead and opportunity data, each containing pre-defined fields. MTS  500  may store, in the same table, database records for one or more tenants—that is, tenants may share a table. Accordingly, database records, in various embodiments, include a tenant identifier that indicates the owner of a database record. As a result, the data of one tenant is kept secure and separate from that of other tenants so that that one tenant does not have access to another tenant&#39;s data, unless such data is expressly shared. 
     In some embodiments, the data stored at data storage  512  is organized as part of a log-structured merge-tree (LSM tree). An LSM tree normally includes two high-level components: an in-memory buffer and a persistent storage. In operation, a database server  514  may initially write database records into a local in-memory buffer before later flushing those records to the persistent storage (e.g., data storage  512 ). As part of flushing database records, the database server  514  may write the database records into new files that are included in a “top” level of the LSM tree. Over time, the database records may be rewritten by database servers  514  into new files included in lower levels as the database records are moved down the levels of the LSM tree. In various implementations, as database records age and are moved down the LSM tree, they are moved to slower and slower storage devices (e.g., from a solid state drive to a hard disk drive) of data storage  512 . 
     When a database server  514  wishes to access a database record for a particular key, the database server  514  may traverse the different levels of the LSM tree for files that potentially include a database record for that particular key. If the database server  514  determines that a file may include a relevant database record, the database server  514  may fetch the file from data storage  512  into a memory of the database server  514 . The database server  514  may then check the fetched file for a database record having the particular key. In various embodiments, database records are immutable once written to data storage  512 . Accordingly, if the database server  514  wishes to modify the value of a row of a table (which may be identified from the accessed database record), the database server  514  writes out a new database record to the top level of the LSM tree. Over time, that database record is merged down the levels of the LSM tree. Accordingly, the LSM tree may store various database records for a database key where the older database records for that key are located in lower levels of the LSM tree then newer database records. 
     Database servers  514 , in various embodiments, are hardware elements, software routines, or a combination thereof capable of providing database services, such as data storage, data retrieval, and/or data manipulation. Such database services may be provided by database servers  514  to components (e.g., application servers  522 ) within MTS  500  and to components external to MTS  500 . As an example, a database server  514  may receive a database transaction request from an application server  522  that is requesting data to be written to or read from data storage  512 . The database transaction request may specify an SQL SELECT command to select one or more rows from one or more database tables. The contents of a row may be defined in a database record and thus database server  514  may locate and return one or more database records that correspond to the selected one or more table rows. In various cases, the database transaction request may instruct database server  514  to write one or more database records for the LSM tree—database servers  514  maintain the LSM tree implemented on database platform  510 . In some embodiments, database servers  514  implement a relational database management system (RDMS) or object oriented database management system (OODBMS) that facilitates storage and retrieval of information against data storage  512 . In various cases, database servers  514  may communicate with each other to facilitate the processing of transactions. For example, database server  514 A may communicate with database server  514 N to determine if database server  514 N has written a database record into its in-memory buffer for a particular key. 
     Application platform  520 , in various embodiments, is a combination of hardware elements and software routines that implement and execute CRM software applications as well as provide related data, code, forms, web pages and other information to and from user systems  550  and store related data, objects, web page content, and other tenant information via database platform  510 . In order to facilitate these services, in various embodiments, application platform  520  communicates with database platform  510  to store, access, and manipulate data. In some instances, application platform  520  may communicate with database platform  510  via different network connections. For example, one application server  522  may be coupled via a local area network and another application server  522  may be coupled via a direct network link. Transfer Control Protocol and Internet Protocol (TCP/IP) are exemplary protocols for communicating between application platform  520  and database platform  510 , however, it will be apparent to those skilled in the art that other transport protocols may be used depending on the network interconnect used. 
     Application servers  522 , in various embodiments, are hardware elements, software routines, or a combination thereof capable of providing services of application platform  520 , including processing requests received from tenants of MTS  500 . Application servers  522 , in various embodiments, can spawn environments  524  that are usable for various purposes, such as providing functionality for developers to develop, execute, and manage applications (e.g., business logic). Data may be transferred into an environment  524  from another environment  524  and/or from database platform  510 . In some cases, environments  524  cannot access data from other environments  524  unless such data is expressly shared. In some embodiments, multiple environments  524  can be associated with a single tenant. 
     Application platform  520  may provide user systems  550  access to multiple, different hosted (standard and/or custom) applications, including a CRM application and/or applications developed by tenants. In various embodiments, application platform  520  may manage creation of the applications, testing of the applications, storage of the applications into database objects at data storage  512 , execution of the applications in an environment  524  (e.g., a virtual machine of a process space), or any combination thereof. In some embodiments, application platform  520  may add and remove application servers  522  from a server pool at any time for any reason, there may be no server affinity for a user and/or organization to a specific application server  522 . In some embodiments, an interface system (not shown) implementing a load balancing function (e.g., an F5 Big-IP load balancer) is located between the application servers  522  and the user systems  550  and is configured to distribute requests to the application servers  522 . In some embodiments, the load balancer uses a least connections algorithm to route user requests to the application servers  522 . Other examples of load balancing algorithms, such as are round robin and observed response time, also can be used. For example, in certain embodiments, three consecutive requests from the same user could hit three different servers  522 , and three requests from different users could hit the same server  522 . 
     In some embodiments, MTS  500  provides security mechanisms, such as encryption, to keep each tenant&#39;s data separate unless the data is shared. If more than one server  514  or  522  is used, they may be located in close proximity to one another (e.g., in a server farm located in a single building or campus), or they may be distributed at locations remote from one another (e.g., one or more servers  514  located in city A and one or more servers  522  located in city B). Accordingly, MTS  500  may include one or more logically and/or physically connected servers distributed locally or across one or more geographic locations. 
     One or more users (e.g., via user systems  550 ) may interact with MTS  500  via network  540 . User system  550  may correspond to, for example, a tenant of MTS  500 , a provider (e.g., an administrator) of MTS  500 , or a third party. Each user system  550  may be a desktop personal computer, workstation, laptop, PDA, cell phone, or any Wireless Access Protocol (WAP) enabled device or any other computing device capable of interfacing directly or indirectly to the Internet or other network connection. User system  550  may include dedicated hardware configured to interface with MTS  500  over network  540 . User system  550  may execute a graphical user interface (GUI) corresponding to MTS  500 , an HTTP client (e.g., a browsing program, such as Microsoft&#39;s Internet Explorer™ browser, Netscape&#39;s Navigator™ browser, Opera&#39;s browser, or a WAP-enabled browser in the case of a cell phone, PDA or other wireless device, or the like), or both, allowing a user (e.g., subscriber of a CRM system) of user system  550  to access, process, and view information and pages available to it from MTS  500  over network  540 . Each user system  550  may include one or more user interface devices, such as a keyboard, a mouse, touch screen, pen or the like, for interacting with a graphical user interface (GUI) provided by the browser on a display monitor screen, LCD display, etc. in conjunction with pages, forms and other information provided by MTS  500  or other systems or servers. As discussed above, disclosed embodiments are suitable for use with the Internet, which refers to a specific global internetwork of networks. It should be understood, however, that other networks may be used instead of the Internet, such as an intranet, an extranet, a virtual private network (VPN), a non-TCP/IP based network, any LAN or WAN or the like. 
     Because the users of user systems  550  may be users in differing capacities, the capacity of a particular user system  550  might be determined one or more permission levels associated with the current user. For example, when a user is using a particular user system  550  to interact with MTS  500 , that user system  550  may have capacities (e.g., user privileges) allotted to that user. But when an administrator is using the same user system  550  to interact with MTS  500 , the user system  550  may have capacities (e.g., administrative privileges) allotted to that administrator. In systems with a hierarchical role model, users at one permission level may have access to applications, data, and database information accessible by a lower permission level user, but may not have access to certain applications, database information, and data accessible by a user at a higher permission level. Thus, different users may have different capabilities with regard to accessing and modifying application and database information, depending on a user&#39;s security or permission level. There may also be some data structures managed by MTS  500  that are allocated at the tenant level while other data structures are managed at the user level. 
     In some embodiments, a user system  550  and its components are configurable using applications, such as a browser, that include computer code executable on one or more processing elements. Similarly, in some embodiments, MTS  500  (and additional instances of MTSs, where more than one is present) and their components are operator configurable using application(s) that include computer code executable on processing elements. Thus, various operations described herein may be performed by executing program instructions stored on a non-transitory computer-readable medium and executed by processing elements. The program instructions may be stored on a non-volatile medium such as a hard disk, or may be stored in any other volatile or non-volatile memory medium or device as is well known, such as a ROM or RAM, or provided on any media capable of staring program code, such as a compact disk (CD) medium, digital versatile disk (DVD) medium, a floppy disk, and the like. Additionally, the entire program code, or portions thereof, may be transmitted and downloaded from a software source, e.g., over the Internet, or from another server, as is well known, or transmitted over any other conventional network connection as is well known (e.g., extranet, VPN, LAN, etc.) using any communication medium and protocols (e.g., TCP/IP, HTTP, HTTPS, Ethernet, etc.) as are well known. It will also be appreciated that computer code for implementing aspects of the disclosed embodiments can be implemented in any programming language that can be executed on a server or server system such as, for example, in C, C+, HTML, Java, JavaScript, or any other scripting language, such as VBScript. 
     Network  540  may be a LAN (local area network), WAN (wide area network), wireless network, point-to-point network, star network, token ring network, hub network, or any other appropriate configuration. The global internetwork of networks, often referred to as the “Internet” with a capital “I,” is one example of a TCP/IP (Transfer Control Protocol and Internet Protocol) network. It should be understood, however, that the disclosed embodiments may utilize any of various other types of networks. 
     User systems  550  may communicate with MTS  500  using TCP/IP and, at a higher network level, use other common Internet protocols to communicate, such as HTTP, FTP, AFS, WAP, etc. For example, where HTTP is used, user system  550  might include an HTTP client commonly referred to as a “browser” for sending and receiving HTTP messages from an HTTP server at MTS  500 . Such a server might be implemented as the sole network interface between MTS  500  and network  540 , but other techniques might be used as well or instead. In some implementations, the interface between MTS  500  and network  540  includes load sharing functionality, such as round-robin HTTP request distributors to balance loads and distribute incoming HTTP requests evenly over a plurality of servers. 
     In various embodiments, user systems  550  communicate with application servers  522  to request and update system-level and tenant-level data from MTS  500  that may require one or more queries to data storage  512 . In some embodiments, MTS  500  automatically generates one or more SQL statements (the SQL query) designed to access the desired information. In some cases, user systems  550  may generate requests having a specific format corresponding to at least a portion of MTS  500 . As an example, user systems  550  may request to move data objects into a particular environment  524  using an object notation that describes an object relationship mapping (e.g., a JavaScript object notation mapping) of the specified plurality of objects. 
     Example Computer System 
     Turning now to  FIG.  6   , a block diagram of an exemplary computer system  600 , which may implement various elements discussed herein, including MTS  500 , and/or user system  550 , is depicted. Computer system  600  includes a processor subsystem  680  that is coupled to a system memory  620  and I/O interfaces(s)  640  via an interconnect  660  (e.g., a system bus). I/O interface(s)  640  is coupled to one or more I/O devices  650 . Although a single computer system  600  is shown in  FIG.  6    for convenience, system  600  may also be implemented as two or more computer systems operating together. 
     Processor subsystem  680  may include one or more processors or processing units. In various embodiments of computer system  600 , multiple instances of processor subsystem  680  may be coupled to interconnect  660 . In various embodiments, processor subsystem  680  (or each processor unit within  680 ) may contain a cache or other form of on-board memory. 
     System memory  620  is usable store program instructions executable by processor subsystem  680  to cause system  600  perform various operations described herein. System memory  620  may be implemented using different physical memory media, such as hard disk storage, floppy disk storage, removable disk storage, flash memory, random access memory (RAM—SRAM, EDO RAM, SDRAM, DDR SDRAM, RAMBUS RAM, etc.), read only memory (PROM, EEPROM, etc.), and so on. Memory in computer system  600  is not limited to primary storage such as memory  620 . Rather, computer system  600  may also include other forms of storage such as cache memory in processor subsystem  680  and secondary storage on I/O Devices  650  (e.g., a hard drive, storage array, etc.). In some embodiments, these other forms of storage may also store program instructions executable by processor subsystem  680 . 
     I/O interfaces  640  may be any of various types of interfaces configured to couple to and communicate with other devices, according to various embodiments. In one embodiment, I/O interface  640  is a bridge chip (e.g., Southbridge) from a front-side to one or more back-side buses. I/O interfaces  640  may be coupled to one or more I/O devices  650  via one or more corresponding buses or other interfaces. Examples of I/O devices  650  include storage devices (hard drive, optical drive, removable flash drive, storage array, SAN, or their associated controller), network interface devices (e.g., to a local or wide-area network), or other devices (e.g., graphics, user interface devices, etc.). In one embodiment, computer system  600  is coupled to a network via a network interface device  650  (e.g., configured to communicate over WiFi, Bluetooth, Ethernet, etc.). 
     *** 
     The present disclosure includes references to “embodiments,” which are non-limiting implementations of the disclosed concepts. References to “an embodiment,” “one embodiment,” “a particular embodiment,” “some embodiments,” “various embodiments,” and the like do not necessarily refer to the same embodiment. A large number of possible embodiments are contemplated, including specific embodiments described in detail, as well as modifications or alternatives that fall within the spirit or scope of the disclosure. Not all embodiments will necessarily manifest any or all of the potential advantages described herein. 
     This disclosure may discuss potential advantages that may arise from the disclosed embodiments. Not all implementations of these embodiments will necessarily manifest any or all of the potential advantages. Whether an advantage is realized for a particular implementation depends on many factors, some of which are outside the scope of this disclosure. In fact, there are a number of reasons why an implementation that falls within the scope of the claims might not exhibit some or all of any disclosed advantages. For example, a particular implementation might include other circuitry outside the scope of the disclosure that, in conjunction with one of the disclosed embodiments, negates or diminishes one or more the disclosed advantages. Furthermore, suboptimal design execution of a particular implementation (e.g., implementation techniques or tools) could also negate or diminish disclosed advantages. Even assuming a skilled implementation, realization of advantages may still depend upon other factors such as the environmental circumstances in which the implementation is deployed. For example, inputs supplied to a particular implementation may prevent one or more problems addressed in this disclosure from arising on a particular occasion, with the result that the benefit of its solution may not be realized. Given the existence of possible factors external to this disclosure, it is expressly intended that any potential advantages described herein are not to be construed as claim limitations that must be met to demonstrate infringement. Rather, identification of such potential advantages is intended to illustrate the type(s) of improvement available to designers having the benefit of this disclosure. That such advantages are described permissively (e.g., stating that a particular advantage “may arise”) is not intended to convey doubt about whether such advantages can in fact be realized, but rather to recognize the technical reality that realization of such advantages often depends on additional factors. 
     Unless stated otherwise, embodiments are non-limiting. That is, the disclosed embodiments are not intended to limit the scope of claims that are drafted based on this disclosure, even where only a single example is described with respect to a particular feature. The disclosed embodiments are intended to be illustrative rather than restrictive, absent any statements in the disclosure to the contrary. The application is thus intended to permit claims covering disclosed embodiments, as well as such alternatives, modifications, and equivalents that would be apparent to a person skilled in the art having the benefit of this disclosure. 
     For example, features in this application may be combined in any suitable manner. Accordingly, new claims may be formulated during prosecution of this application (or an application claiming priority thereto) to any such combination of features. In particular, with reference to the appended claims, features from dependent claims may be combined with those of other dependent claims where appropriate, including claims that depend from other independent claims. Similarly, features from respective independent claims may be combined where appropriate. 
     Accordingly, while the appended dependent claims may be drafted such that each depends on a single other claim, additional dependencies are also contemplated. Any combinations of features in the dependent that are consistent with this disclosure are contemplated and may be claimed in this or another application. In short, combinations are not limited to those specifically enumerated in the appended claims. 
     Where appropriate, it is also contemplated that claims drafted in one format or statutory type (e.g., apparatus) are intended to support corresponding claims of another format or statutory type (e.g., method). 
     Because this disclosure is a legal document, various terms and phrases may be subject to administrative and judicial interpretation. Public notice is hereby given that the following paragraphs, as well as definitions provided throughout the disclosure, are to be used in determining how to interpret claims that are drafted based on this disclosure. 
     References to a singular form of an item (i.e., a noun or noun phrase preceded by “a,” “an,” or “the”) are, unless context clearly dictates otherwise, intended to mean “one or more.” Reference to “an item” in a claim thus does not, without accompanying context, preclude additional instances of the item. A “plurality” of items refers to a set of two or more of the items. 
     The word “may” is used herein in a permissive sense (i.e., having the potential to, being able to) and not in a mandatory sense (i.e., must). 
     The terms “comprising” and “including,” and forms thereof, are open-ended and mean “including, but not limited to.” 
     When the term “or” is used in this disclosure with respect to a list of options, it will generally be understood to be used in the inclusive sense unless the context provides otherwise. Thus, a recitation of “x or y” is equivalent to “x or y, or both,” and thus covers 1) x but not y, 2) y but not x, and  3 ) both x and y. On the other hand, a phrase such as “either x or y, but not both” makes clear that “or” is being used in the exclusive sense. 
     A recitation of “w, x, y, or z, or any combination thereof” or “at least one of . . . w, x, y, and z” is intended to cover all possibilities involving a single element up to the total number of elements in the set. For example, given the set [w, x, y, z], these phrasings cover any single element of the set (e.g., w but not x, y, or z), any two elements (e.g., w and x, but not y or z), any three elements (e.g., w, x, and y, but not z), and all four elements. The phrase “at least one of . . . w, x, y, and z” thus refers to at least one element of the set [w, x, y, z], thereby covering all possible combinations in this list of elements. This phrase is not to be interpreted to require that there is at least one instance of w, at least one instance of x, at least one instance of y, and at least one instance of z. 
     Various “labels” may precede nouns or noun phrases in this disclosure. Unless context provides otherwise, different labels used for a feature (e.g., “first circuit,” “second circuit,” “particular circuit,” “given circuit,” etc.) refer to different instances of the feature. Additionally, the labels “first,” “second,” and “third” when applied to a feature do not imply any type of ordering (e.g., spatial, temporal, logical, etc.), unless stated otherwise. 
     The phrase “based on” or is used to describe one or more factors that affect a determination. This term does not foreclose the possibility that additional factors may affect the determination. That is, a determination may be solely based on specified factors or based on the specified factors as well as other, unspecified factors. Consider the phrase “determine A based on B.” This phrase specifies that B is a factor that is used to determine A or that affects the determination of A. This phrase does not foreclose that the determination of A may also be based on some other factor, such as C. This phrase is also intended to cover an embodiment in which A is determined based solely on B. As used herein, the phrase “based on” is synonymous with the phrase “based at least in part on.” 
     The phrases “in response to” and “responsive to” describe one or more factors that trigger an effect. This phrase does not foreclose the possibility that additional factors may affect or otherwise trigger the effect, either jointly with the specified factors or independent from the specified factors. That is, an effect may be solely in response to those factors, or may be in response to the specified factors as well as other, unspecified factors. Consider the phrase “perform A in response to B.” This phrase specifies that B is a factor that triggers the performance of A, or that triggers a particular result for A. This phrase does not foreclose that performing A may also be in response to some other factor, such as C. This phrase also does not foreclose that performing A may be jointly in response to B and C. This phrase is also intended to cover an embodiment in which A is performed solely in response to B. As used herein, the phrase “responsive to” is synonymous with the phrase “responsive at least in part to.” Similarly, the phrase “in response to” is synonymous with the phrase “at least in part in response to.” 
     Within this disclosure, different entities (which may variously be referred to as “units,” “circuits,” other components, etc.) may be described or claimed as “configured” to perform one or more tasks or operations. This formulation—[entity] configured to [perform one or more tasks]—is used herein to refer to structure (i.e., something physical). More specifically, this formulation is used to indicate that this structure is arranged to perform the one or more tasks during operation. A structure can be said to be “configured to” perform some task even if the structure is not currently being operated. Thus, an entity described or recited as being “configured to” perform some task refers to something physical, such as a device, circuit, a system having a processor unit and a memory storing program instructions executable to implement the task, etc. This phrase is not used herein to refer to something intangible. 
     In some cases, various units/circuits/components may be described herein as performing a set of task or operations. It is understood that those entities are “configured to” perform those tasks/operations, even if not specifically noted. 
     The term “configured to” is not intended to mean “configurable to.” An unprogrammed FPGA, for example, would not be considered to be “configured to” perform a particular function. This unprogrammed FPGA may be “configurable to” perform that function, however. After appropriate programming, the FPGA may then be said to be “configured to” perform the particular function. 
     For purposes of United States patent applications based on this disclosure, reciting in a claim that a structure is “configured to” perform one or more tasks is expressly intended not to invoke 35 U.S.C. § 112(f) for that claim element. Should Applicant wish to invoke Section 112(f) during prosecution of a United States patent application based on this disclosure, it will recite claim elements using the “means for” [performing a function] construct. 
     Different “circuits” may be described in this disclosure. These circuits or “circuitry” constitute hardware that includes various types of circuit elements, such as combinatorial logic, clocked storage devices (e.g., flip-flops, registers, latches, etc.), finite state machines, memory (e.g., random-access memory, embedded dynamic random-access memory), programmable logic arrays, and so on. Circuitry may be custom designed, or taken from standard libraries. In various implementations, circuitry can, as appropriate, include digital components, analog components, or a combination of both. Certain types of circuits may be commonly referred to as “units” (e.g., a decode unit, an arithmetic logic unit (ALU), functional unit, memory management unit (MMU), etc.). Such units also refer to circuits or circuitry. 
     The disclosed circuits/units/components and other elements illustrated in the drawings and described herein thus include hardware elements such as those described in the preceding paragraph. In many instances, the internal arrangement of hardware elements within a particular circuit may be specified by describing the function of that circuit. For example, a particular “decode unit” may be described as performing the function of “processing an opcode of an instruction and routing that instruction to one or more of a plurality of functional units,” which means that the decode unit is “configured to” perform this function. This specification of function is sufficient, to those skilled in the computer arts, to connote a set of possible structures for the circuit. 
     In various embodiments, as discussed in the preceding paragraph, circuits, units, and other elements may be defined by the functions or operations that they are configured to implement. The arrangement and such circuits/units/components with respect to each other and the manner in which they interact form a microarchitectural definition of the hardware that is ultimately manufactured in an integrated circuit or programmed into an FPGA to form a physical implementation of the microarchitectural definition. Thus, the microarchitectural definition is recognized by those of skill in the art as structure from which many physical implementations may be derived, all of which fall into the broader structure described by the microarchitectural definition. That is, a skilled artisan presented with the microarchitectural definition supplied in accordance with this disclosure may, without undue experimentation and with the application of ordinary skill, implement the structure by coding the description of the circuits/units/components in a hardware description language (HDL) such as Verilog or VHDL. The HDL description is often expressed in a fashion that may appear to be functional. But to those of skill in the art in this field, this HDL description is the manner that is used transform the structure of a circuit, unit, or component to the next level of implementational detail. Such an HDL description may take the form of behavioral code (which is typically not synthesizable), register transfer language (RTL) code (which, in contrast to behavioral code, is typically synthesizable), or structural code (e.g., a netlist specifying logic gates and their connectivity). The HDL description may subsequently be synthesized against a library of cells designed for a given integrated circuit fabrication technology, and may be modified for timing, power, and other reasons to result in a final design database that is transmitted to a foundry to generate masks and ultimately produce the integrated circuit. Some hardware circuits or portions thereof may also be custom-designed in a schematic editor and captured into the integrated circuit design along with synthesized circuitry. The integrated circuits may include transistors and other circuit elements (e.g. passive elements such as capacitors, resistors, inductors, etc.) and interconnect between the transistors and circuit elements. Some embodiments may implement multiple integrated circuits coupled together to implement the hardware circuits, and/or discrete elements may be used in some embodiments. Alternatively, the HDL design may be synthesized to a programmable logic array such as a field programmable gate array (FPGA) and may be implemented in the FPGA. This decoupling between the design of a group of circuits and the subsequent low-level implementation of these circuits commonly results in the scenario in which the circuit or logic designer never specifies a particular set of structures for the low-level implementation beyond a description of what the circuit is configured to do, as this process is performed at a different stage of the circuit implementation process. 
     The fact that many different low-level combinations of circuit elements may be used to implement the same specification of a circuit results in a large number of equivalent structures for that circuit. As noted, these low-level circuit implementations may vary according to changes in the fabrication technology, the foundry selected to manufacture the integrated circuit, the library of cells provided for a particular project, etc. In many cases, the choices made by different design tools or methodologies to produce these different implementations may be arbitrary. 
     Moreover, it is common for a single implementation of a particular functional specification of a circuit to include, for a given embodiment, a large number of devices (e.g., millions of transistors). Accordingly, the sheer volume of this information makes it impractical to provide a full recitation of the low-level structure used to implement a single embodiment, let alone the vast array of equivalent possible implementations. For this reason, the present disclosure describes structure of circuits using the functional shorthand commonly employed in the industry.