Abstract:
A method, computer program product, and system for optimizing service pools supporting resource sharing and enforcing SLAs, to minimize service restart. A computer processor determines a first resource to be idle, wherein a service instance continues to occupy the first resource that is idle. The processor adds the first resource to a resource pool, wherein the service instance continues to occupy the first resource as a global standby service instance on the first resource. The processor receives a request for a resource, wherein the request for the resource includes a global name associated with a service that corresponds to the global standby service instance, and the processor allocates, from the resource pool, the first resource having the global standby service instance, based on the request for the resource that includes the global name associated with the service corresponding to the global standby service instance.

Description:
RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 14/089,886, filed on Nov. 26, 2013, status pending. 
    
    
     STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINT INVENTOR 
     The following disclosure(s) are submitted under 35 U.S.C. 102(b)(1)(A): DISCLOSURE(S): Product release Announcement titled “IBM Platform Symphony V6.1 enables scalable, high-performance grid services for parallel compute- and data-intensive analytic applications”, for a product made publicly available on Dec. 14, 2012, page(s) 2, Planned Availability Date section, (www.ibm.com/common/ssi/ShowDoc.wss?docURL-/common/ssi/rep_ca/6/897/ENUS212-426/index.html&amp;lang=en&amp;request_locale=en). 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of operation of aggregate computing resources, and more particularly to dynamic resource sharing and service level agreement (SLA) enforcement. 
     Environments in which computing resources are shared by multiple entities, such as an enterprise environment, typically have multiple applications that consume services from grid resources. Each application can use more than one type of service, and may be associated with one or multiple consuming entities, for example, different business units within an enterprise organization. 
     Management of shared computing resources can involve providing an agreed-to level of resources, referred to as a service level agreement (SLA), for each entity sharing resources within an interconnected consolidation of computing resources known as a cluster or grid. Management of shared computing resources also requires efficiency in utilization of resource assets, minimizing idle time, but enabling dynamic sharing of resources as demands of consuming entities vary with respect to time. 
     In a distributed computing grid environment, client applications submit workload requests to a workload manager. The workload requests generate sessions that include tasks that the workload manager schedules on available resources that can be “deserved” or shared. A “deserved” level or resources aligns with the agreed-to resource level of a SLA, for an application associated with a consuming entity of a distributed computing grid. Shared resources may be allowed under SLA management when resources are idle such that a client application may consume resources above the agreed-to level of its SLA as long as resource demand is below capacity. However, shared resources may be reclaimed by another client application, when its workload demand increases and resources previously idle are now required. 
     When a client application associated with an entity of the distributed computing grid, submits a large workload to a workload manager, the workload manager will request additional resources to execute the high demand of workload. The resource manager consults a resource plan to determine the agreed-to resources and allocates the agreed-to level of resources to the workload manager for the client application. If additional resources are required by the submitted workload and resources are idle, the resource manager may allocate additional resources to the requesting workload manager to perform workload demand in excess of the agreed-to resource level. 
     An area of concern in maintaining high efficiency levels in a shared computing grid is the time needed to start or initialize a service instance, especially for cases in which the service instance has to load a large software library or a large amount of data at initialization. If such service instances are started and terminated frequently, performance will suffer for the application calling the service instances. 
     When resource consumption of a service operating on a specific resource, referred to as a “slot”, is very large, there is a risk of overloading the slot. Avoiding situations in which multiple services with large memory consumption occupy a slot at the same time, is preferred to prevent performance issues resulting from the operating system resorting to swapping in order to free memory. 
     BRIEF SUMMARY 
     Embodiments of the present invention disclose a method, computer program product, and system for optimizing service pools supporting resource sharing and enforcing SLAs, to minimize service restart. A computer processor determines a first resource to be idle, wherein a service instance continues to occupy the first resource that is idle. The computer processor returns the first resource determined to be idle, to a resource pool, wherein the service instance continues to occupy the first resource as a global standby service instance on the first resource, added to the resource pool. The computer processor receives a request for a resource, wherein the request for the resource includes a global name associated with a service that corresponds to the global standby service instance, and the computer processor allocates, from the resource pool, the first resource having the global standby service instance, based on the request for the resource that includes the global name associated with the service corresponding to the global standby service instance. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a functional block diagram illustrating a distributed computing grid environment, in accordance with one embodiment of the present invention. 
         FIG. 2  is a functional block diagram of an exemplary illustration for service instance reuse across client applications, in accordance to an embodiment of the present invention. 
         FIG. 3  illustrates operational steps of a global standby program, operating on a middleware layer of a managing server within the distributed computing grid environment of  FIG. 1 , in accordance with an embodiment of the present invention. 
         FIG. 4  depicts a block diagram of components of a managing server capable of operating the global standby program, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention recognize that service pool resizing enables being able to share resources amongst different applications and different entity consumers of grid resources. Applications submitting workload requests for services include tasks that are run within service instances. Embodiments also recognize that initializing service instances can affect performance, specifically when the service instance has to load a large software library or a large quantity of data and/or the service instance is terminated and restarted frequently. 
     An approach suggested to address the potential performance issues includes using a standby service, in which a service instance initiated on a resource is not terminated after a scheduled task running within the service instance is complete. However, embodiments of the present invention recognize that the service instance remaining on the resource can only be reused by the same application that initiated the service instance, thus limiting its effectiveness and value. Embodiments of the present invention include a global standby service in which a service is identified by a global name, use by workload resource requests, such that other applications in the distributed computing grid environment using the same service are able to re-use the actively running service instance on an available resource, regardless of which application initiated the service instance. 
     As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer-readable medium(s) having computer readable program code/instructions embodied thereon. 
     Any combination of computer-readable media may be utilized. Computer-readable media may be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of a computer-readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     A computer-readable signal medium may include a propagated data signal with computer-readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer-readable signal medium may be any computer-readable medium that is not a computer-readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. 
     Program code embodied on a computer-readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. 
     Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on a user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
     Aspects of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer-readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The present invention will now be described in detail with reference to the Figures.  FIG. 1  is a functional block diagram illustrating distributed computing grid environment  100 , in accordance with one embodiment of the present invention. Distributed computing grid environment  100  includes managing server  120 , computing grid  140 , and computing devices  160  and  170 , all interconnected through network  150 . Computing grid  140  includes resource slots  145 . Managing server  120  includes workload manager  125 , resource manager  130 , and global standby program  300 . Managing server  120  also includes middleware, which is computer software that provides services to software applications beyond those available from the operating system. Middleware is commonly used for software that enables communication and management of data in distributed applications, and as such workload manager  125 , resource manager  130  and global standby program  300  can operate within the middleware of managing server  120 . 
     Network  150  can be, for example, a local area network (LAN), a wide area network (WAN) such as the Internet, or a combination of the two, and can include wired or wireless connections. In general, network  150  can be any combination of connections and protocols that will support communications via various channels between client computing devices  160  and  170 , managing server  120  and computing grid  140 , in accordance with an embodiment of the present invention. 
     Computing devices  160  and  170  are components of distributed computing grid environment  100  capable of operating one or more applications that submit workload sessions that include tasks to workload manager  125 . Computing device  160  includes client  110 , and computing device  170  includes client  112 . Clients  110  and  112  are application programs capable of submitting session requests to workload manager  125 , to run the tasks within respective sessions on resource slots  145  available in computing grid  140 . 
     Computing devices  160  and  170  can each be a laptop computer, a specialized mobile computer server, a tablet, or netbook personal computer (PC), a personal digital assistant (PDA), a smart phone, or any computing device capable of downloading and operating an app from a network connection. In general, computing devices  160  and  170  are representative of any programmable electronic device or combination of programmable electronic devices capable of executing machine-readable program instructions. Computing devices  160  and  170  include internal and external hardware components, as depicted and described in further detail with respect to  FIG. 4 . 
     Computing grid  140  is an aggregate interconnected group of resources that work together to perform tasks scheduled on the resource slots  145 . The resources of computing grid  140  are managed by resource manager  130  and the tasks run on the resources of computing grid  140  are scheduled and managed by workload manager  125 . Computing grid  140  includes resource slots  145  which represent the “slots” within computing grid  140 , which are units of resources to which tasks can be scheduled to be run. Resource slots  145  are managed by resource manager  130  and tasks are scheduled on resource slots  145  by workload manager  125 . 
     Tasks are computations or logic functions that can be executed in parallel in a computing cluster or grid, such as distributed computing grid environment  100 . Groupings of one or more tasks form a “session”, also referred to as a “job”, which acts as a container for tasks. Services provide a software function to a client application, and an application may use different types of services, each providing a unique function. Tasks run within a running instance of a service are referred to as a service instance. A service instance is an application program that can be reused to perform multiple tasks. 
     Managing server  120  is a computing device that controls the assignment of resources to various client application requests, such as clients  110  and  112  operating on computing devices  160  and  170  respectively. Managing server  120  is a server computing device that can be a desktop computer, laptop computer, a specialized computer server, a client computer, tablet, or netbook personal computer (PC), a personal digital assistant (PDA), a smart phone, a mainframe computer, a web server computer, or a networked server computer. Further, managing server  120  can represent computing systems utilizing clustered computers and components to act as single pools of seamless resources when accessed through network  150 , as is common in data centers and with cloud computing applications. In general, managing server  120  is representative of any programmable electronic device or combination of programmable electronic devices capable of executing machine-readable program instructions. Managing server  120  may include internal and external hardware components, as depicted and described in further detail with respect to  FIG. 4 . 
     Managing server  120  includes workload manager  125 , resource manager  130 , and global standby program  300 . Managing server  120  includes an operating system (OS) program layer, a middleware program layer, and an application program layer. The middleware program layer can include workload manager  125 , resource manager  130 , and global standby program  300 . Resource manager  130  is a component of distributed computing environment  100  that controls allocation and adjustment of resources used to perform tasks as submitted by client applications with access to computing grid  140 . Resource manager  130  responds to resource demands from workload manager  125  by allocating at least a minimum agreed-to level of resources of computing grid  140  if required by the demand. 
     The level of allocation is based on a policy or an established SLA of resources “deserved” by a client application when the application submits workload requests to workload manager  125 . “Deserved” resources are the quantity of resources that must be allocated to a client application by the resource manager, as specified in the agreed-to policy or SLA, based on the level of workload demand. If the workload demand is high enough, resource manager  130  allocates the deserved level of resources to workload manager  125 , possibly having to reclaim resources being shared by other applications. If resource use is below the capacity level, resource manager  130  may determine if there are idle resources from under-using entities, and based on the workload demand, may allocate resources from an idle resource pool to workload manager  125  for use in executing the workload demand. This practice is known as “sharing” resources and makes idle resources available to entities with high demand that can benefit from use of additional available resources. In this manner resources are used to achieve higher efficiencies in an environment in which resources are shared, such as distributed computing grid environment  100 . 
     Workload manager  125  resides on the middleware of managing server  120 . Workload manager  125  manages and schedules the tasks included in session requests received from a client application, such as client application  110 . Workload manager  125  requests resources from resource manager  130  in response to receiving workload demand from client application  110 . Workload manager  125  determines the scheduling priority of tasks given the available resources and tasks are scheduled to resource “slots”, such as resource slots  145 , and run to completion on the scheduled slot. When workload manager  125  has no additional tasks to run on the allocated slots for client application  110 , the slots are returned to resource manager  130  and become part of a pool of idle resources available to allocate to other applications as needed. 
     Global standby program  300  is a program operating within the middleware of managing server  120 . Global standby program  300  works in conjunction with resource manager  130  in interpreting the service type for which resource requests are made by currently running client applications. In one embodiment of the present invention, global standby program  300  may be a separate program called by resource manager  130 . In other embodiments, global standby program  300  may be integrated as part of resource manager  130 . Global standby program  300  enables a global standby service that runs on the resources within computing grid  140  of distributed computing grid environment  100 . Global standby program  300  enables the sharing and reuse of resources which are returned to resource pools and are occupied with service instances that remain available, to improve performance efficiency by avoiding delays from service instance restarts on resources. 
     Global standby program  300  enables a service instance of a service requested by a client application that is running on a resource to remain running after the executing task has completed or becomes idle. The service instance is not terminated by global standby program  300  when the resource slot becomes idle, but is returned to the idle resource pool of resource manager  130  with the service instance still occupying the resource slot. 
     Global standby program  300  uses a global name for each global service instance type used by applications submitting workload to be performed on resource slots  145  of computing grid  140 . Global names are defined in the application definition file of client applications and identify the services used by the application. Workload managers include the service global name when submitting workload requests. The global name is included when the workload manager  125  requests resources from resource manager  130 , for its workload demand. Resource manager  130  uses the global name to identify resource slots occupied by service instances matching the global name. 
     Resource manager  130  preferentially allocates resource slots with matching global name service instances to meet the resource request of workload manager  125 , if such resource slots are available. As a second priority, resource manager  130  allocates resource slots that are free of any service instances occupying the slot, from the idle resource pool. As a low priority, if resource manager  130  is unable to meet the resource request for a workload manager demand by matching resource slots occupied with service instances matching the global name of the requested service, or is unable to meet deserved resource levels by allocating resource slots free of service instances, resource manager  130  terminates service instances occupying resource slots of the idle resource pool (or reclaimed slots) and allocates the resource slots to fulfill the demand of the requesting workload manager. 
     Service instances are cached for reuse once an application does not need them anymore. The service instance is terminated only if there are insufficient empty slots to meet the demand for applications that can&#39;t use the cached service instance. 
     Initiation of a service instance may be lengthy, especially if it requires loading a large software library or large quantities of data. Performance issues may result from frequent starting and terminating of service instances. Global standby program  300  allows service instances occupying resource slots to be reused without the performance issues of frequent starting and terminating, and in addition allows service instances occupying resource slots in idle resource pools to be used by other applications requiring the same service. 
       FIG. 2  is a functional block diagram of an exemplary illustration for service instance reuse across client applications, in accordance to an embodiment of the present invention. Idle resource pool  210  is a collection of resource slots, hereafter referred to as slots that are not allocated to an application and are not executing tasks. The slots in  FIG. 2  are depicted as ovals. Idle resource pool  210  includes slots that are available for resource manager  130  to allocate to workload manager  125  to meet the workload requests of a client application, such as client application  110 . Slots from idle resource pool  210  are allocated as needed, and when the slots are idle, they are returned to idle resource pool  210 . 
     As depicted, the slots in idle resource pool  210  are all occupied by a service instance. The applications in the exemplary illustration use one or both of two services available. Global standby service-A  215  is the portion of idle resource pool  210  having slots occupied by service instances of service-A. Global standby service-B  217  is the portion of idle resource pool  210  having slots occupied by service instances of service-B. The service instances occupying the slots are available to run tasks using the respective services. 
     Client application service pool  220  includes one pool of slots on which service instances of a service are running to execute tasks. Client application service pool  220  includes service-A pool  225  containing slots with running services instances of service-A. Similarly, client application service pool  230  and client application service pool  240  include two pools of slots running service instances on which tasks are executing. Client application service pool  230  includes service-A pool  235  and service-B pool  237  each containing slots running service instances of their respective service. Client application service pool  240  includes service-A pool  245  and service-B pool  247 , each containing slots running service instances of their respective service. 
     In an embodiment of the present invention, the client application associated with client application service pool  230  submits additional workload to its corresponding workload manager, for example, resource manager  130  ( FIG. 1 ), and the workload manager responds by requesting additional resources from the workload manager, for example, workload manager  125 . The client application, for example, client application  110 , indicates the service needed by including the global name of the service, for example service-B, when submitting the additional workload. The workload manager includes the global name of service-B in the request for resources sent to the resource manager, and the resource manager determines if slots in idle resource pool  210  match the global name of service-B, needed for the requested resources. If a match is found, the slots occupied by service-B instances, which match the global name, are allocated by resource manager  130  to workload manager  125  to perform the service on scheduled tasks. 
     If a client application, such as client application  112  ( FIG. 1 ), associated with client application service pool  240 , has completed tasks running on slots in service-B pool  247 , the slots become idle and workload manager  125  returns the idle slots to resource manager  130 . The service-B instances on the idle slots are not terminated, but continue to occupy the returned slots, and the slots are added to global standby service-B  217  of idle resource pool  210 . 
       FIG. 3  is a flowchart depicting the operational steps of global standby program  300 , in accordance to an embodiment of the present invention. Global standby program  300  works in conjunction with resource manager  130  and workload manager  125 . Global standby program  300  receives a request for resources that includes a global name of a service (step  310 ). Global standby program  300  receives a request for resources needed by a client application and receives a global name associated with the service needed to perform workload tasks. The global name associated with the service is defined in the application definition file of each application that uses the service. This allows a service instance of the global named service to be consistently used across other applications submitting workload to the resources of the computing grid. 
     For example, global standby program  300  receives a request for slots from idle resource pool  210  ( FIG. 2 ), from client application  110 , and receives a global name of a service, such as service-B ( FIG. 2 ). Global standby program  300  recognizes that the resource request intends to use service-B to complete a workload for which the slots are requested. 
     Global standby program  300  determines if resources with matching global standby service instances are available, and determining that resources with matching global standby service instances are available (decision step  330 , “YES” branch), global standby program  300  allocates resources with matching global standby service instances (step  360 ). Global standby program  300  uses the global name associated with a service to identify resources with a matching service instance occupying the resource. 
     For example, global standby program  300  uses the global name associated with a service, such as service-B, that was received in the resource request from workload manager  125 , and identifies if there are slots in idle resource pool  210  that have service-B service instances running on the slots. Determining that there are slots with service-B service instances in idle resource pool  210 , global standby program  300  allocates the slots with the matching service-B service instances to workload manager  125 . 
     Having allocated the resources with matching global standby service instances, the tasks are run and completed within the service instances of the resources. Global standby program  300  determines if the resources are idle, and confirming the resources of completed tasks are idle (decision step  350 , “YES” branch), global standby program  300  receives idle resources retaining the global standby service instances (step  380 ). Global standby program  300  does not terminate the service instances of the returned resources; however, the service instances are cached and remain available to be used by the same application or another application to perform tasks requiring this service. The resources with global standby service instances are returned to an idle resource pool of the resource manager and global standby program  300  ends. 
     For example, global standby program  300  determines if resources are idle. In one embodiment of the present invention, the task scheduled on the resource slot may inform global standby program  300  that the task is complete, or is in a waiting state, and the resource slot is available. Global standby program  300  receives control of an idle resource running a service instance of service-B. Global standby program  300  does not terminate the service instance, leaving the service instance of service-B occupying the resource slot. Global standby program  300  returns the idle program with the service instance of service-B to idle resource pool  210 , making the slot available. Having a running service instance of service-B on the slot makes using the slot for service-B much more efficient, avoiding data loading delays and clearing activities associated with frequent starting and ending actions, respectively. 
     If global standby program  300  determines that resources with matching global standby service instances are not available, (decision step  320 , “NO” branch), global standby program  300  determines if resources free of service instances are available, and determining that resources free of service instances are available (decision step  330 , “YES” branch), global standby program  300  allocates resources free of service instances (step  370 ). 
     For example, global standby program  300  preferentially allocates resources to workload manager  125  that have standby service instances running that match the service identified by the global name received with the workload request. Having determined that resource slots having global standby service instances matching the service associated with the global name, such as service-B, are not available, global standby program  300  determines if there are resource slots available that are free of global standby service instances. Resource slots free of service instances may be used to initiate any service; however, performance penalties may be experienced due to loading requirements at the start of the service instance. This preference leaves resource slots occupied by other global standby service instances, available for application resource requests that require other service instances, for example, service-A. 
     If global standby program  300  determines that resources free of service instances are not available (decision step  330 , “NO” branch), global standby program  300  terminates the global standby service instances and allocates the resources with service instances cleared (step  340 ). Having exhausted preferences of allocating resources, global standby program  300  terminates the global standby service instances occupying the resources, freeing the resources to initiate the required service instances without potentially overloading the resources by leaving a previously running service instance occupying the resource as a new service instance of a different service is started. 
     As resources complete scheduled tasks, global standby program  300  determines if resources are idle, and determining that resources are not idle global standby program  300  monitors to determine if resources are idle (decision step  350 , “NO” branch). 
       FIG. 4  depicts a block diagram of components of a managing host server  400 , capable of operating global standby program  300 , in accordance with an illustrative embodiment of the present invention. It should be appreciated that  FIG. 4  provides only an illustration of one implementation and does not imply any limitations with regard to the environments in which different embodiments may be implemented. Many modifications to the depicted environment may be made. 
     Server computer  400  includes communications fabric  402 , which provides communications between computer processor(s)  404 , memory  406 , persistent storage  408 , communications unit  410 , and input/output (I/O) interface(s)  412 . Communications fabric  402  can be implemented with any architecture designed for passing data and/or control information between processors (such as microprocessors, communications and network processors, etc.), system memory, peripheral devices, and any other hardware components within a system. For example, communications fabric  402  can be implemented with one or more buses. 
     Memory  406  and persistent storage  408  are computer-readable storage media. In this embodiment, memory  406  includes random access memory (RAM)  414  and cache memory  416 . In general, memory  406  can include any suitable volatile or non-volatile computer-readable storage media. 
     Global standby program  300  is stored in persistent storage  408  for execution by one or more of the respective computer processors  404  via one or more memories of memory  406 . In this embodiment, persistent storage  408  includes a magnetic hard disk drive. Alternatively, or in addition to a magnetic hard disk drive, persistent storage  408  can include a solid state hard drive, a semiconductor storage device, read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, or any other computer-readable storage media that is capable of storing program instructions or digital information. 
     The media used by persistent storage  408  may also be removable. For example, a removable hard drive may be used for persistent storage  408 . Other examples include optical and magnetic disks, thumb drives, and smart cards that are inserted into a drive for transfer onto another computer-readable storage medium that is also part of persistent storage  408 . 
     Communications unit  410 , in these examples, provides for communications with other data processing systems or devices, including resources of distributed computing grid environment  100 . In these examples, communications unit  410  includes one or more network interface cards. Communications unit  410  may provide communications through the use of either or both physical and wireless communications links. Global standby program  300  may be downloaded to persistent storage  408  through communications unit  410 . 
     I/O interface(s)  412  allows for input and output of data with other devices that may be connected to managing host server  400 . For example, I/O interface  412  may provide a connection to external devices  418  such as a keyboard, keypad, a touch screen, and/or some other suitable input device. External devices  418  can also include portable computer-readable storage media such as, for example, thumb drives, portable optical or magnetic disks, and memory cards. Software and data used to practice embodiments of the present invention, e.g., global standby program  300 , can be stored on such portable computer-readable storage media and can be loaded onto persistent storage  408  via I/O interface(s)  412 . I/O interface(s)  412  also connect to a display  420 . 
     Display  420  provides a mechanism to display data to a user and may be, for example, a computer monitor. 
     The programs described herein are identified based upon the application for which they are implemented in a specific embodiment of the invention. However, it should be appreciated that any particular program nomenclature herein is used merely for convenience, and thus the invention should not be limited to use solely in any specific application identified and/or implied by such nomenclature. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.