This application is a continuation application claiming priority to Ser. No. 10/843,932, filed May 11, 2004, now U.S. Pat. No. 8,856,793, issued Oct. 7, 2014. 
    
    
     BACKGROUND 
     The invention relates generally to computer systems, and deals more particularly with a technique to schedule computer program jobs for periodic execution. 
     Many types of computer program jobs are scheduled for periodic execution. These program job update databases, maintain databases (i.e. trim logs, purge old documents, etc.), backup data, perform other “batch jobs”, and perform routine system or user maintenance. For example, a database backup program can be scheduled to execute at midnight every day, and a database maintenance program can be scheduled to execute at six o&#39;clock PM every Sunday. Various computer resources such as processor(s), RAM, disk storage, and I/O (input/output) may be needed to execute the program. However, occasionally, the computer has many jobs to execute at one time, and there may be inadequate resources to execute them all promptly or effectively. A deficiency of even one resource can impede the execution of the job. 
     It was known to evaluate the availability of computer resources before beginning to execute a program job. If the availability is low, then the execution of the program job can be delayed until more resources become available. U.S. Pat. No. 6,578,005 discloses a technique to change an execution schedule when resources become unavailable. U.S. Pat. No. 6,418,459 discloses a technique to schedule tasks based on current resource availability. It was also known for an application to report its resource needs to a scheduler so the scheduler can determine if sufficient resources are currently available to execute the application. 
     An object of the present invention is to schedule computer program jobs or other types of applications for execution at a regular time when sufficient computer resources are likely to be available. 
     SUMMARY OF THE INVENTION 
     The invention resides in a system, method and program for scheduling a program for periodic execution. The program requires a computer resource for execution. The historic utilization or availability of the resource is determined and recorded at a multiplicity of times a day. Subsequently, a request is received to schedule a program for execution on the day at a specific time and daily thereafter at the specific time or weekly or monthly thereafter on the day at the specific time. In response, the record of the historic utilization or availability of the resource is checked for the day at approximately the specific time to determine if there has been sufficient availability or a predetermined minimum amount of availability of the resource in the past on the day at approximately the specific time. If so, the program is scheduled for execution on the day and specific time and daily thereafter at the specific time or weekly or monthly thereafter on the day at the specific time as requested. If not, the program is not scheduled for execution on the day at the specific time. 
     According to another feature of the present invention, if there was not sufficient availability or the predetermined minimum amount of availability of the resource in the past on the day and time, then another time on the day close to specific time is automatically determined when there was sufficient availability of the resource in the past to execute the program. Then, an operator is notified of the other time on the day. The operator indicates whether the other time on the day is acceptable. If so, the program is scheduled for execution at the other time on the day and daily thereafter at the other time or weekly or monthly thereafter on the day at the other time. 
     According to another feature of the present invention, the request is to schedule a program for execution during a time window of a specific day. In response, the record of the historic utilization or availability of the resource for the time window on the day is checked to determine if there has been sufficient availability or a predetermined minimum amount of availability of the resource in the past during the time window on the day. If so, the program is scheduled for execution at a time within the time window on the day when there was sufficient availability or a predetermined minimum amount of availability of the resource in the past and daily thereafter at the time or weekly or monthly thereafter on the day at the time as requested. If not, the program is not scheduled for execution during the time window. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a block diagram of a computer system in which the present invention is incorporated. 
         FIG. 2  is a flow chart illustrating a computer resource monitoring program according to the present invention. 
         FIG. 3  is a flow chart illustrating a job scheduling program according to the present invention. 
         FIG. 4  is a flow chart illustrating a job execution program according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described in detail with reference to the figures.  FIG. 1  illustrates a computer system generally designated  10  in which the present invention is installed and executed. Computer system  10  comprises a processor  12 , a RAM  14 , an operating system  16 , disk storage  20  and a keyboard  22  through which an administrator can schedule program jobs for periodic execution as described below. Multiple job programs  32 ,  34 ,  36  and  38  are stored in disk storage  20 . Computer system  10  also comprises a job scheduling program  40  which schedules each of the job programs  32 ,  34 ,  36  and  38  for periodic execution. For example, job program  32  is scheduled for execution at midnight every Monday, job program  34  is scheduled for execution every day at 5 PM and job program  36  is scheduled for execution every Wednesday at noon. Job  38  is yet to be scheduled. Computer system  10  also comprises a resource monitoring program  42  monitors availability of computer resources at every unit of time, for example, every minute of every day. These computer resource comprise the CPU  12 , RAM  14 , and storage  20 , but could include other computer resources as well. Computer resource monitoring program  42  then averages and records the “historic” resource utilization or availability at every unit of time. The resource monitoring program  42  is further described below with reference to  FIG. 2 . Resource availability/utilization tends to follow time patterns. This is because certain times of day are busier than others due to normal work schedules, user demand, and system maintenance activities. Also, many existing program jobs are scheduled for periodic execution at common times. Computer system  10  also includes a job execution program  44  which attempts to execute jobs when scheduled. 
     A computer readable storage medium or storage device, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
     When a user or application requests to schedule a new program job for periodic execution, the request may specify a desired regular time and day for execution or a desired time window on the day for execution. In such a case, job scheduling program  40  predicts, based on the historic average resource availability records, whether sufficient resources will likely be available in the future at the desired time and day. If not, job scheduling program  40  will notify the requestor, and identify an alternate time, near to the desired time when sufficient resources are likely to be available (based on the historic availability records). The requestor can then accept or reject this alternate, regular time for execution. Thus, job scheduling program  40  recommends or selects the regular day and time for execution of each of the new program job such as job  38  when it is expected that there are sufficient resources available to promptly and effectively execute the program job. This is further described below with reference to  FIG. 3 . 
     Meanwhile, a job execution program  44  is running. When the time comes for execution of a scheduled job, the job execution program  44  determines if there are sufficient resources available to execute the scheduled job. If so, the job execution program  44  notifies the operating system to execute the job. If not, the job execution program  44  determines another time to execute the job when it is likely, based on historical availability or utilization data, that there will be sufficient resources to execute the job. This is further described below with reference to  FIG. 4 . 
       FIG. 2  illustrates in more detail the resource monitoring program  42  which gathers and averages the historic data of resource availability. Resource monitoring program  40  periodically (for example, every five minutes or preferably, every minute or less) queries the operating system for availability or utilization data for the processor  12 , RAM  14  and storage  20  (steps  98  and  100 ). The system availability or utilization data is generated by known hardware and microcode functions. For example, Unix, Windows NT and IBM zSeries systems all include such hardware and microcode. The hardware and microcode within a zSeries system is further described in US Patent Application entitled “System and Method to Monitor Amount of Usage of Applications in Logical Partitions” Ser. No. 10/613,779 filed Jul. 1, 2003 by Mathias, et al., which patent application is hereby incorporated by reference into the present disclosure. In the Unix system, the resource monitoring program obtains this availability or utilization data by calling a known vmstat function. In the Windows system, this availability or utilization data is obtained by calling a Performance Monitor function. In the z/OS operating system, the resource monitoring program  42  obtains this availability or utilization data by calling a known RMF function. There are similar functions in other operating systems which will obtain the availability or utilization data. If there is new availability or utilization data, then resource monitoring program  40  parses the data to separate out the availability or utilization data for each computer resource of interest (step  104 ). Then, for each resource of interest, resource monitoring program  40  performs the following steps  106 - 110  with the respective availability or utilization data. If this is the first availability or utilization data for resources of interest for the current time unit, for example, the 1:15 PM to 1:16 PM on Monday time unit, (decision  106 , no branch), then the resource monitoring program enters a new record for this resource into an availability or utilization database  45  specifying the resource availability, day and time (step  108 ). The resource availability or utilization may be expressed as a percentage of total resources available such as 10% of the CPU, and 15% of the RAM and 20% of the storage. Alternately, the resource availability or utilization may be expressed as an absolute amount of resources available or used such as ten MIPs of CPU, five megabytes of RAM or one hundred gigabytes of storage. (For purposes of the present invention, if the data obtained from the system hardware and microcode indicates resource utilization, then the resource monitoring function  42 , job scheduling program  40  and job execution program  44  can subtract the utilization amount for each resource from the respective total system resources to determine the availability of each resource.) Referring again to decision  106 , yes branch, if there was prior availability or utilization data for computer resource for the current time unit, then resource monitoring program  40  averages the current availability or utilization data for this time unit with the prior availability or utilization data for this time unit for the resource, and updates the corresponding record (step  110 ). The average availability or utilization data computed in step  110  will only reflect the last month&#39;s (or other relevant period&#39;s) availability or utilization data; older data is purged before the averaging occurs in step  110 . If there is availability or utilization data for another of the resources yet to be processed in steps  106 - 111  (decision  112 , yes branch), then resource monitoring program  40  loops back to step  104 . Otherwise, resource monitoring program waits for the next time unit to occur (step  98 ), to proceed to step  100  where it queries the operating system for availability or utilization data. 
       FIG. 3  illustrates the operation of job scheduling program  40  in more detail. After invoking job scheduling program  40  (step  198 ), an application or an administrator using a computer keyboard or mouse requests a specific, regular time and day to schedule the program job  38  for execution, such as every Monday at midnight, every day at 5 PM, the first Monday of every month at 5 PM or the tenth of every month at 5 PM (step  200 ). The application or administrator can also specify the minimum availability of each type of resource required or recommended for the program job. In the absence of such a specification, default values will apply, where the default values are general guidelines for executing program jobs. The minimum availability levels are stored in a program job requirements file  225 . Then, job scheduling program  40  reads the historic resource availability records from the availability or utilization data base  45  to determine if the minimum threshold of resources of each type has been available at the requested day and time unit (step  204 ). In the foregoing examples, this would be the Monday 12:00 AM to 12:01 AM time unit, the everyday 5:00 PM to 5:01 PM time unit, the first Monday every month 6:00 PM to 6:01 PM time unit or the tenth of every month 5:00 PM to 5:01 PM time unit. If the minimum threshold of availability of each resource has not been met on average in the past month during this time unit (decision  206 , no branch), then job scheduling program  40  identifies alternate, periodic time slots to execute the program job (step  208 ). Job scheduling program  40  identifies the alternate time slots based on what time unit within one hour (or other relevant time period) of the requested time or time window has had the most resource availability on the average during the last month. The job scheduling program obtains this information from the resource availability records from the availability or utilization data base  45 . Referring again to decision  206 , yes branch, where the historic, average availability of resources is equal to or greater than the respective thresholds for all the resources of interest during the specified day and time, job scheduling program  40  schedules the program job by making an entry in a job scheduling file  210 ; the entry includes the name of the program job and regular day and time for execution (step  208 ). 
     In another embodiment of the present invention, the application or administrator requests that the program job  38  be scheduled for execution within a specified time window of a day, for example between 5 PM and 6 PM every Monday (or between 5 PM and 6 PM daily or between 5 PM and 6 PM every tenth of every month). In this other embodiment, in step  204 , the job scheduling program reads the availability or utilization database  45  to identify a specific time unit within the window when there are the predetermined minimum amount of resources available. For example, it may be the case that between 5:10 PM and 5:11 PM there are sufficient resources to execute the program job, and this time unit can be scheduled. Alternately, job scheduling program  44  reads the availability or utilization database  45  to identify the specific time within the window when there is the most availability of the resources, and the availability exceeds the minimum thresholds. In this alternate embodiment of the present invention, that will be the time when the program job is scheduled for execution. 
       FIG. 4  illustrates ongoing operation of job execution program  40  to initiate execution of scheduled jobs. Job execution program  40  periodically (for example, every second) reads the job scheduling file  210  (step  220 ) to determine if the time has arrived to execute any program jobs (decision  222 ). If not, then the job execution program  40  waits for the next time period to check the job scheduling file again (step  224 ). However, if there is a program job scheduled for execution at the current time, then job execution program  40  determines if there are sufficient computer resources currently available to execute the job. If this is the first time that the program job will be executed, then there is no historical data on how much computer resources of each type are used to execute the program job. So, in this case, the job execution program  40  determines if the current availability of all of the computer resources equals or exceeds the respective minimum specified by the requestor in step  200  or the default values, in absence of such a specification. If sufficient resources of all types are currently available (decision  230 , yes branch), then the job execution program  40  notifies the operating system to execute the program job. If not, then the job execution program  40  determines when, during the next hour (or other relevant time period) that sufficient computer resources are likely to be available (step  240 ). In another embodiment of the present invention, the job execution program searches for the best time within the next hour to execute this job. The “best” time is the time when the resource availability is expected to be the highest, and is expected to exceed the minimum thresholds. Both determinations are based on the historical availability records within the availability or utilization data base  45 . In still another embodiment of the present invention, if sufficient resources are not currently available to execute the job (decision  230 , no branch), job execution program  40  reschedules/delays planned execution of the job by a predetermined amount, for example five minutes (step  240 ). This delay amount can be preprogrammed into job execution program or specified by the “owner/requestor” of the job. In either case, when it is time to execute the rescheduled job, the job execution program  44  will repeat decisions  222  and  230  to determine if there are sufficient resources available then. If not, then the planned execution is delayed another five minutes or until another optimum execution time as determined from the historical availability records. 
     During the first execution of each program job, the job execution program  40  monitors the amount of utilization of each resource, and stores the utilization data in the program job requirements file  225  replacing the specification made by the requestor in step  200  or the default values in the absence of the specification. This monitoring is performed by a query to the Performance Monitor function in the case of the Windows operating system, the vmstat function in the case of the Unix operating system, or the RMF function in the case of the z/OS operating system. All of these functions will return the utilization of each resource caused by the job. For subsequent executions of this same program job, to determine if there are sufficient resources available in decision  230 , the job execution program will query the Performance Monitor function in the case of the Windows operating system, the vmstat function in the case of the Unix operating system or the RMF function in the case of the z/OS operating system to determine the current availability of each resource. Then, the job execution program will compare the utilization requirements data for the job (from the program job requirements file  225 ) to the current availability. If the current availability of all the resources is greater than requirements of all the respective resources for the job, then the job execution program  44  will request that the operating system execute the job. 
     Based on the foregoing, a system, method and program for scheduling jobs for periodic execution have been disclosed. However, numerous modifications and substitutions can be made without deviating from the scope of the present invention. Therefore, the present invention has been disclosed by way of example and not limitation, and reference should be made to the following claims to determine the scope of the present invention.
A method and system for scheduling, for periodic execution, a program requiring a computer hardware resource for execution. A computer determines and records historic utilization or availability of the resource multiple times a day. The computer subsequently receives a request to schedule the program for execution on the day at a specified time and (a) daily, (b) weekly, or (c) monthly at the specified time, and in response, the computer determines if there has been historical availability of the resource exceeding a predetermined availability threshold on the day at approximately the specified time to execute the program, and if so, schedule the program for execution on the day at the specified time and (i) daily, (ii) weekly, or (iii) monthly thereafter, as requested, and if not, not schedule the program for execution on the day at the specified time or (i) daily, (ii) weekly, or (iii) monthly thereafter, as requested.