Abstract:
An application event collector which is embodied in computer software that collects event-based data. The collector follows a process which includes the steps of: (a) storing definitions of event-marking instructions that have been embedded in the software application, each instruction being capable, when enabled, of collecting event-based data, and the definitions identifying the software application in which the instructions have been embedded and the type of data collected by the instructions; (b) selecting, prior to or during execution of the application, a subset of the event-marking instructions and enabling those instructions; and (c) detecting the enabled event-marking instructions, during execution of the software application, and collecting the data specified by the enabled instructions. The application is divided into layers, each of which may have event-marking instructions embedded in it. These event marking instructions are capable of selectively collecting a some or all of a number of data items and a user can select which of these data items are to be collected. The user can also disable collection of data items.

Description:
This is a continuation of application Ser. No. 08/052,227, filed Apr. 22, 1993, now abandoned, which was a continuation of Ser. No. 07/485,372, filed Feb. 26, 1990, now abandoned. 
    
    
     Reference to Microfiche Appendix 
     The application includes a microfiche appendix pursuant to 37 CFR §1.96(b) containing 14 microfiche having 660 frames. 
     BACKGROUND OF THE INVENTION 
     The invention relates to software application event collection systems. 
     Most software application event collection systems are &#34;timer based,&#34; i.e., they collect data from an application program at specified time intervals. Because random parts of the application are executed at any given time, the actual frequency of events occurring in the collected data must be calculated as an average or estimated frequency. On the other hand, so-called &#34;event based&#34; evaluation systems gather data at specified locations in the application and thus collect and report on the actual frequency of events, not on an estimated frequency. Software debugging systems, for example, are one type of event based evaluation systems. In debugging systems, the application to be debugged is &#34;instrumented&#34; at points of interest with calls to service routines in another application which does the actual debugging. The points of interest are often referred to as &#34;breakpoints&#34; and include, for example, the beginnings and endings of subroutines. Each time the instrumented subroutine executes, the data related to the event is collected as part of the evaluation. 
     SUMMARY OF THE INVENTION 
     In general, the invention features an application event collector which is embodied in computer software that collects event-based data for a number of purposes described below in connection with a presently preferred embodiment. The collector follows a process which includes the steps of: (a) storing definitions of event-marking instructions that have been embedded in the software application, each instruction being capable, when enabled, of collecting event-based data, and the definitions identifying the software application in which the instructions have been embedded and the type of data collected by the instructions; (b) selecting, prior to or during execution of the application, a subset of the event-marking instructions and enabling those instructions; and (c) detecting the enabled event-marking instructions, during execution of the software application, and collecting the data specified by the enabled instructions. 
     In preferred embodiments, the application is divided into layers, each of which may have event-marking instructions embedded in it. These event marking instructions are capable of selectively collecting a some or all of a number of data items and a user can select which of these data items are to be collected. The user can also disable collection of data items. To these ends, the definitions of the event-marking instructions include identification of the software layer in which the instruction is embedded and the definitions include classes of event-marking instructions and data items that may be selected. 
     The collector provides several benefits, including a &#34;real-time&#34; collection capability, i.e., collection of event data from an application as the application is running in its intended environment. Real-time collection is contrasted with &#34;modelled&#34; evaluations, i.e., collection of event data from an application as the application is running in a simulated environment. This real-time collection capability allows recording of only those events specified by the user via the schedule user interface and the collector is able to capture the actual frequency of the data at runtime. Thus, significant runtime overhead (both computational and storage related) is eliminated. Likewise, the collector is able to collect event-based data from any combination of layers within a software application. 
     The collector further provides collection of event-based data that can serve as the basis for tuning software application runtime performance. For example, the invention can provide the &#34;workload analysis&#34; used to fine tune a database as described in connection with the Physical Database Designer of a application Ser. No. 07/485,376, now abandoned, by Michael E. Gioielli et al. entitled PHYSICAL DATABASE DESIGN SYSTEM and filed on even date with this application. 
     The collector further provides a basis for planning hardware resources (also referred to as &#34;capacity planning&#34;). That is, the collector can determine the computational and storage needs of an application. The resulting data can be input, for example, to the DECcp version 1.1 capacity planning product. 
     The collector further provides a basis for debugging applications and logging errors within the applications. And finally, the collector is designed to operate with minimal performance impact on the application from which it is gathering data, and also to allow users to customize what data is collected. Thus, it can be used in both production and development environments. 
     Other advantages and features will become apparent from the following description, and from the claims. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a block diagram of a layered application. 
     FIG. 2 is a block diagram of the components of an application event collector according to the present invention. 
     FIG. 3 is a flow chart describing the general operation of the application event collector. 
     FIG. 4 is a flow chart describing the operation of a service routine call of Collector, i.e., INIT. 
     FIG. 5 is a block diagram of a data structure maintained by INIT. 
     FIG. 6 is a flow chart describing the operation of a service routine call of Collector, i.e., EVENT. 
     FIG. 7 is a flow chart describing the operation of a service routine call of Collector, i.e., EVENTW. 
     FIG. 8 is a flow chart describing the operation of a service routine call of Collector, i.e., EVENTPRV. 
     FIG. 9 is a flow chart describing the operation of a service routine call of Collector, i.e., START --  EVENT. 
     FIG. 10 is a flow chart describing the operation of a service routine call of Collector, i.e., START --  EVENTW. 
     FIG. 11 is a flow chart describing the operation of a service routine call of Collector, i.e., START --  EVENTPRV. 
     FIG. 12 is a flow chart describing the operation of a service routine call of Collector, i.e., END --  EVENT. 
     FIG. 13 is a flow chart describing the operation of a service routine call of Collector, i.e., END --  EVENTW. 
     FIG. 14 is a flow chart describing the operation of a service routine call of Collector, i.e., END --  EVENTPRV. 
     FIG. 15 is a block diagram of a facility definition data structure. 
     FIG. 16 is a block diagram of an item data structure. 
     FIG. 17 is a block diagram of a facility data structure. 
     FIG. 18 is a flow chart describing the operation of store group data, one aspect of the facility selection process. 
     FIG. 19 is a flow chart describing the operation of facility extract, one aspect of the schedule collection process. 
    
    
     The application event collector of the present invention (herein referred to as the &#34;collector&#34;) is embodied in a layered software application that collects, formats, and reports on the event based data it gathers from other layered software applications that contain service routine calls to collector. An application is made up of one or more &#34;layers.&#34; For example, an application layer can be application code (e.g., customer code) or layered product code (e.g., VAX ACMS, VAX Rdb/VMS, 3rd party software, etc.). Referring to FIG. 1, an application 2 having four layers is shown in block diagram form. The arrangement of the layers can be hierarchical, e.g., beginning with a VAX All-in-1 layer 3, and proceeding through a VAX ACMS (Application Control Management System) layer 4, a customer code layer 5, and a VAXRdb/VMS database layer 6. The source code in each layer in the application must be instrumented with calls to the collection service routines described below in order to collect event-based data from the layer. Once the layers are instrumented, the user can manage data collection via the schedule user interface described below in connection with FIG. 2. 
     Since the goal of operating with minimal impact on the application is as important when data collection is turned off as when it is turned on, the source code in each layer of the application determines which events are currently being collected by various &#34;event collection flags.&#34; If, for example, an event collection flag is set, then the application layer issues a call to a collection service routine. Otherwise, the application layer does not issue a call to the service routine, and, thus minimizes the overhead incurred when data collection is turned off. Specifically, the overhead is limited to two instructions: one compare instruction to determine if the flag is set and one branch instruction to continue execution of the application layer. 
     The collector further achieves the objective of minimizing overhead by providing a system that allows a user to determine which layers he can collect data from, and what events and data items are available within each layer. Thus, the user can collect data from only those layers that he is interested in. For example, if the user is interested in tuning his current VAX Rdb/VMS database, he can specify that he wants data collected from the Rdb/VMS database layer of the application only. To further minimize overhead, the user can specify one or more of various event &#34;classes&#34; to be collected within each layer. For example, if the user is interested in collecting only workload data from the VAX Rdb/VMS layer, he can specify a class of data that includes only workload events and data items. 
     The user can then use the collector to determine what applications are currently running on a computer system, e.g., a VAXcluster. Having determined which applications are running, the user can schedule a data collection that he specified above. In addition, he can schedule how long to collect the data specified and where to store the data that is collected, as well as specific applications from which to collect the data. For example, if the user knows what applications interface with the VAX Rdb/VMS database layer he is interested in, then he can specify data collection from those applications only. Also, if he knows that the applications from which he wants to collect data typically run between 8 am and 5 pm, then he can limit the duration of the collection accordingly. 
     Thus, the collector is a system in which an application programmer creates a &#34;facility definition&#34;, i.e., defines a number of events, a number of data items associated with each event, and a number of classes of events and data items that his application contains. The programmer does this in addition to instrumenting the application code with the various service routine calls that are common to event based evaluation systems. Once the facility definition is complete, a user can create a &#34;facility selection&#34; i.e. select events, data items, and classes from among a number of facility definitions for a number of applications. The user can also select when to turn a facility selection on (i.e., when to begin collecting data for a selected application) and when to turn a facility selection off (i.e., when to stop collecting data for a selected application). One advantage of this approach is that the application for which the facility selection is turned off incurs no overhead, i.e., the application does not actually execute the service routine calls despite the fact that the application itself is fully instrumented. 
     Referring to FIG. 2, a collector 10 includes a software application having a number of application layers 12. One example of an application layer 12 is the software for a bank automatic teller machine (ATM). Each application layer 12 includes a number of &#34;events&#34; i.e., the occurrence of one or more operations. Events are divided into two types: those that have a start and an end (referred to as &#34;duration&#34; events) and those that simply occur (referred to as &#34;point&#34; events). Examples of a duration event are basic ATM transactions such as checking a balance, depositing funds, or withdrawing funds. One example of a point event in an ATM application layer is the execution of an error handling procedure. 
     Each event in the application layer 12 is further associated with a number of data items, e.g., the standard resource utilization items listed in Table 1 below. It is the data relating to each of these items that is collected at the execution of each event by the collector, if the standard resource utilization items are defined for each event in the facility definition. 
     
                       TABLE 1______________________________________BIO           Number of buffered I/O operationsDIO           Number of direct I/O operationsPAGEFAULTS    Number of hard and soft page faultsPAGEFAULT.sub.-- IO         Number of hard page faultsCPU           Amount of CPU timeCURRENT.sub.-- PRIO         Current priority of the processVIRTUAL.sub.-- SIZE         Number of virtual pages currently         mapped for the processWS.sub.-- SIZE         Current working set sizeWS.sub.-- PRIVATE         Number of pages in the working set         that are private to the processWS.sub.-- GLOBAL         Number of pages in the working set         that are shared among processes______________________________________ 
    
     In order to collect the data described above, the application layer 12 is connected to a registrar process 14 which handles communication between the application layer and an administration database 16 that contains a description of the events and data items to be collected for the application layer. The events and data items for the application layer 12 are defined in a &#34;facility definition&#34; which stored in the administration database 16. Likewise, a &#34;facility selection&#34; (also stored in the administration database 16) defines subsets of the events and data items defined in the facility definitions in order to allow a user to customize the data that is collected. 
     The application layer 12 is further connected via the registrar 14 to a schedule user interface 18, which is also connected to the administration database 16. Communication between the schedule user interface 18, the administration database 16, the registrar 14, and the application layer 12 controls, for example, when a facility selection is turned on, i.e., when a user schedules a collection that tells the application layer to start collecting data, and when a facility selection is turned off, i.e., when a user cancels a collection before its scheduled end time. One particular advantage of this arrangement is that it minimizes any reduction in performance of the application layer 12 when data is not being collected. 
     Finally, the collected data, i.e., the data associated with the events and data items specified in the facility selection, is stored in a data collection file 20. The user can format the data in the data collection file 20 and produce various reports as described later in the specification. First, however, an overview of the collection process, including the steps taken by the application layer programmer and the steps taken by the user, is provided below in connection with the flow chart of FIG. 3. 
     Referring to FIG. 3, an application programmer &#34;instruments&#34; his application layer 12 with service routine calls that collect data and store it in the data collection file 20 (step 100). Such calls indicate, for example, when an application layer is initialized, when an event begins, and when an event ends. When executed, the application layer 12, determines which events and data items are selected for the application layer 12, and begins the collection. Also at the start of a collection, the registrar 14 manages communications with various subroutines to set up records in the data collection file 20 in which to store the data which the application layer 12 is collecting. 
     To the above ends, the programmer creates a &#34;facility definition&#34; for the application layer 12 and stores the definition in the administration database 16 (step 102). Users view these facility definitions to assist them in scheduling data collection. From the information in the facility definitions, a user then creates a &#34;facility selection&#34; in which he names the facilities and classes of events and items for each facility from which he wishes to collect data (step 104). Having completed his selection, the user next schedules data collection through the schedule user interface 18 (step 106), i.e., references the facility selection created in step 104 or a previously created facility selection. The user then schedules a collection via the schedule user interface 18 and executes the application layer 12, which causes the application layer and registrar 14 to collect data for the events defined in step 100 and to store the data in the data collection file 20 (step 108). Finally, the user formats the data stored in the data collection file 20 (step 110), and prints the formatted data in report form (step 112). A detailed description of each of these steps is provided below. 
     Instrumenting the Application Code 
     As noted above in connection with FIG. 3, in the first step of the data collection process, the application programmer instruments the source code of application layer 12 with service routine calls. Table 2 below lists some of the service routine calls recognized by Collector, each of which serves a different purpose. For example, the INIT service routine call identifies one application as a layer (also referred to as a facility) and informs the registrar process 14 that the layer is able to collect data. Once the application layer is so identified, the various EVENT service routine calls define the events within the application layer, i.e., the occurrence of a point event or the start and end of a duration event. Each call from the application layer 12 via the Collector service routines to the registrar 14 further involves a number of error checks to ensure that the application layer passes all of the data necessary for the registrar to conduct the data collection. These and other features of the service routine calls is provided below in connection with FIGS. 4-13. 
     
                       TABLE 2______________________________________END.sub.-- EVENT        Records the end of a duration event        to the data collection fileEND.sub.-- EVENTW        Records the end of a duration event        to the data collection file and waits for        processing to complete before it returnsEVENT        Records the occurrence of a point event        to the data collection fileEVENTW       Records the occurrence of a point event        to the data collection file and waits for        processing to complete before it returnsINIT         Registers an application layer (facility)        with the registrar to enable        data collection from the layerSTART.sub.-- EVENT        Records the start of a duration event        to the data collection fileSTART.sub.-- EVENTW        Records the start of a duration event        to the data collection file and waits for        processing to complete before it returns______________________________________ 
    
     INIT Service Routine Call 
     The first of the several service routine calls described herein is INIT which is instrumented at the prior to the first event for each application layer 12. Its purpose is to inform the registrar 14 that the application layer 12 is running and is able to collect data. An example of the INIT service routine call instrumented in a section of application code is shown below in &#34;Code Example 1&#34;. ##SPC1## 
     The basic operation of INIT is to register the facility with the registrar 14, i.e., inform the registrar that the application layer 12 is running and is enabled to collect data. INIT is illustrated in the flow chart of FIG. 4. First, INIT enables an error condition handler (step 200) to respond to any errors in the list of parameters passed by the application layer 12 when it calls the routine. Next, INIT validates the contents of one or more of the parameters in the list of parameters (step 202), makes certain a collection has not been previously disabled for the application due to an unexpected error, determines whether a collection is enabled (step 204), and determines if the contents of the facility number parameter passed by the application layer 12 are valid (step 206). If the result of any of the tests in steps 202-206 is false, an error is returned to the application layer 12 (step 208). Otherwise, if the result of each of the tests in steps 202-206 is true, then INIT copies the contents of the facility number parameter passed by application layer 12 into a local variable (step 210), validates the contents of the facility version parameter (step 212), and copies the contents of the facility version parameter into a local variable (step 214). If, however, the contents of the facility version parameter are found invalid (step 212), then INIT returns an error to the application layer 12 (step 216). 
     Having initialized and validated the contents of the required parameters passed by the application layer 12, INIT next determines if the application layer has been initialized (step 218), i.e., it uses the contents of the facility number and facility version parameters passed by the application layer to determine whether INIT has been called twice from the same layer within the application layer. To assist in this determination, the registrar process 14 maintains a facility list which contains a facility entry for each application layer that has called INIT and has thus been connected with the registrar. If INIT determines that the application layer has been initialized already, it returns a message to the application layer (step 220), indicating that INIT has already been called from the application layer. Finally, INIT next validates the contents of the registration identification parameter passed by the application layer 12 (step 222). If the identification is valid, INIT copies its contents into a local variable (step 224). Otherwise, if the identification is invalid, INIT returns an error to the application layer (step 226). 
     Next, having validated the contents of most of the parameters, INIT prepares any remaining parameters passed by the application 12 to receive information from the data collection. Specifically, INIT clears the event flags parameters and the item flags parameter passed by the application layer 12 by writing zeros into each of the flags (step 228) and by clearing the status parameter (step 230). Following steps 228 and 230, INIT constructs the resource name (FIG. 2) used to communicate messages from the application layer 12 to the registrar 14. 
     Next, INIT creates a temporary mailbox (step 234) for the application layer 12 which receives start and stop messages from the registrar 14 to control the data collection, e.g., messages to start or cancel a data collection. Then, if the facility is not already entered in the facility list, INIT adds a facility entry to the facility list (step 236). The facility entry is shown in block diagram form in FIG. 5 and includes a facility number 50, event flags 52, an address for the event flags 54, item flags 56, and an address for the item flags 58. Otherwise, INIT assigns values to the event flags 52 and item flags 56 (step 238). 
     In order to create a new facility entry in step 236, INIT first creates the entry and copies the contents of the facility version number parameter to the facility number field 50 of the entry. Likewise, INIT copies the contents of the identification parameter, the addresses of the event flags parameter, and the address of the item flags to their respective fields in the entry. Finally, INIT initializes the entry so that it is available for data collection, sends the facility entry information to the registrar, and sets a flag indicating that the facility has been registered. 
     If a collection is turned on for the current facility, a facility entry already exits. Therefore, INIT updates the existing facility entry as in step 238, or after creating the entry in step 236, INIT sets the contents of the event flags 52, sets the contents of the item flags 56, writes the entry to the data collection file 20, copies the contents of the identification and facility version parameters to the entry. Finally, INIT returns the status of the facility and its data collection to the application layer, e.g., SUCCESS or DISABLED (step 240). 
     EVENT Service Routine Call 
     EVENT is a service routine call instrumented at the occurrence of each asynchronous point event in the application layer 12. Its purpose is to record point event data in the data collection file 20. An example of the EVENT service routine call instrumented in a section of application code is provided below in &#34;Code Example 2&#34;. ##SPC2## 
     In addition, the operation of EVENT when called by the application layer 12 is illustrated in the flow chart of FIG. 6. First, EVENT enables an error condition handler (step 300) to respond to any errors in the parameters passed by the application layer 12 when it calls the routine. Next, EVENT determines if data collection is disabled (step 302). If data collection is disabled, then EVENT returns an error to the application layer 12 (step 304). Otherwise, EVENT validates the required parameters in the list of parameters (step 306) and calls another service routine EVENTPRV (step 308), which validates the contents of the parameters and writes the contents to the facility entry. (EVENTPRV is described below in connection with FIG. 8.) Finally, EVENT returns the status of the call to the application layer (step 310). 
     Analogously, EVENTW is a service routine call instrumented at the occurrence of each synchronous point event in the application layer 12. Its purpose is to record synchronous point event data in the data collection file 20. An example of the EVENTW service routine call instrumented in a section of application layer code is provided above &#34;Code Example 2&#34;. In addition, the operation of EVENTW when called by the application layer 12 is illustrated in the flow chart of FIG. 7 and described below. 
     Referring to FIG. 7, EVENTW first enables an error condition handler (step 400) to respond to any errors in the parameters passed by the application layer 12 when it calls the routine. Then EVENTW determines if data collection is disabled (step 402). If data collection is disabled, then EVENTW returns an error to the application layer 12 (step 404). Otherwise, EVENTW validates the contents of one or more of the parameters in the list of parameters (step 406) and calls the service routine EVENTPRV (step 408) which validates the contents of the parameters and writes the contents to the facility entry. (EVENTPRV is described below in connection with FIG. 8.) Finally, EVENTW returns the status of the call to the application layer (step 410). 
     EVENTPRV Service Routine Call 
     EVENTPRV is a routine called by the EVENT and EVENTW as described above. Its purpose is to enter data collected in the event service routines in the facility entries. To do this, EVENTPRV takes the contents of the parameters it receives from the event service routines, validates them, and copies them into the facility entry. The operation of EVENTPRV is described below in connection with the flow chart of FIG. 8. 
     Referring to FIG. 8, EVENTPRV first enables an error condition handler (step 500) to respond to any errors in the parameters passed by the event service routines. Next, EVENTPRV validates the contents of the facility number parameter (step 502), the contents of the event identification (step 504), and the contents of any optional parameters (step 506). Then EVENTPRV validates each of the optional parameters (step 508), and returns an error to the event service routine for any parameter that is invalid. 
     Having validated the parameters, EVENTPRV next locates the facility entry corresponding to the facility number parameter passed by the event service routine (step 510). If there is no facility entry, EVENTPRV returns an error to the event service routine (step 512). Otherwise, EVENTPRV determines if the event is to be collected (step 514), i.e., whether the flag for the event is set. If the event is not to be collected, EVENTPRV returns an error to the event service routine (step 516). Otherwise, EVENTPRV determines the size of the record needed to hold the collected data (step 518), allocates the space for that record (step 520), and timestamps the record (step 522). Having thus prepared the record, EVENTPRV then copies the contents of the parameters passed by the event service routine into the record (step 524), writes the record to the data collection file 20 (step 526), and returns a successful status, i.e., SUCCESS, to the event service routine (step 528). 
     START --  EVENT Service Routine Call 
     START --  EVENT is a service routine call instrumented at the start of each asynchronous duration event in the application layer 12. Its purpose is to record asynchronous duration event data in the data collection file 20. An example of the START --  EVENT service routine call instrumented in a section of application code is provided above in &#34;Code Example 1.&#34; In addition, the operation of START --  EVENT when called by the application layer 12 is illustrated in the flow chart of FIG. 9 and described below. 
     Referring to FIG. 9, START --  EVENT first enables an error condition handler (step 600) to respond to any errors in the parameters passed by the application layer 12. Next, START --  EVENT determines if data collection is disabled (step 602). If data collection is disabled, then START --  EVENT returns an error to the application layer 12 (step 604). Otherwise, START --  EVENT validates the required parameters (step 606) and calls the routine START --  EVENTPRV (step 608) which is described below in connection with FIG. 11. Finally, START --  EVENT returns a status to the application layer 12 (step 610). 
     Analogously, START --  EVENTW is a service routine call instrumented at the start of each synchronous duration event in the application layer 12. Its purpose is to record synchronous duration event data in the data collection file 20. An example of the START --  EVENTW service routine call instrumented in a section of application layer code is provided above &#34;Code Example 1&#34;. In addition, the operation of START --  EVENTW when called by the application layer 12 is illustrated in the flow chart of FIG. 10 and described below. 
     Referring to FIG. 10, START EVENTW first enables an error condition handler (step 700) to respond to any errors in the parameters passed by the application layer 12. Next, START --  EVENTW determines if data collection is disabled (step 702). If data collection is disabled, then START --  EVENTW returns an error to the application layer 12 (step 704). Otherwise, START --  EVENTW validates the contents of the required parameters (step 706) and calls the routine START --  EVENTPRV (step 708) which is described below in connection with FIG. 11. Finally, START --  EVENTW returns a status to the application layer 12 (step 710). 
     START --  EVENTPRV Service Routine Call 
     Referring to FIG. 11, START --  EVENTPRV first enables an error condition handler (step 800) to respond to any errors in the parameters passed by the start event service routines. Next, START --  EVENTPRV validates the contents of the required parameters (step 802), i.e., the facility number parameter, the contents of the event identification (step 804), and the contents of the handle (step 806). In response to these tests, START --  EVENTPRV returns an error to the start event service routine for any of these parameters that is invalid (step 808). Next, START --  EVENTPRV clears the operating system&#39;s event flag (step 810), and validates the contents of any optional parameters (step 812). 
     Having validated the parameters, START --  EVENTPRV next locates the facility entry corresponding to the facility number parameter passed by the event service routine (step 814). If there is no facility entry, START --  EVENTPRV returns an error to the event service routine which indicates that data is not being collected for the facility (step 816). Otherwise, START --  EVENTPRV determines if the event is to be collected (step 818), i.e., whether the flag for the event is set. If the event is not to be collected, START --  EVENTPRV returns an error to the event service routine (step 820). Otherwise, START --  EVENTPRV determines the size of the record needed to hold the collected data (step 822), allocates the space for that record (step 824), and timestamps the record (step 826). Having thus prepared the record, START --  EVENTPRV then copies the contents of the parameters passed by the event service routine into the record (step 828), writes the record to the data collection file 20 (step 830), and returns a successful status, i.e., SUCCESS, to the event service routine (step 840). 
     END --  EVENT Service Routine Call 
     END --  EVENT is a service routine call instrumented at the end of each asynchronous duration event in the application layer 12. Its purpose is to record duration event data in the data collection file 20. An example of the END --  EVENT service routine call instrumented in a section of application layer code is provided above &#34;Code Example 1&#34;. In addition, the operation of END --  EVENT when called by the application layer 12 is illustrated in the flow chart of FIG. 12 and described below. 
     Referring to FIG. 12, END --  EVENT first enables an error condition handler (step 900) to respond to any errors in the parameters passed by the event service routines. Next, END --  EVENT determines if data collection is enabled (step 902). If data collection is disabled, then END --  EVENT returns an error to the application layer 12 (step 904). Otherwise, END --  EVENT validates the required parameters (step 906). If the required parameters exist, END --  EVENT calls the routine END --  EVENTPRV (step 908) which is described below in connection with FIG. 14. Otherwise, END --  EVENT returns an error to the application layer 12 (step 909). Finally, END --  EVENT returns a status to the application layer 12 (step 910). 
     Analogously, END --  EVENTW is a service routine call instrumented at the end of each synchronous duration event in the application layer 12. Its purpose is to record duration point event data in the data collection file 20. An example of the END --  EVENTW service routine call instrumented in a section of application code is provided above in &#34;Code Example 1&#34;. In addition, the operation of END --  EVENTW when called by the application layer 12 is illustrated in the flow chart of FIG. 13 and described below. 
     Referring to FIG. 13, END --  EVENTW first enables an error condition handler (step 1000) to respond to any errors in the parameters passed by the event service routines. Next, END --  EVENTW determines if data collection is enabled (step 1002). If data collection is disabled, then END --  EVENT returns an error to the application layer 12 (step 1004). Otherwise, END --  EVENTW checks for the existence of the required parameters (step 1006). If the required parameters exist, END --  EVENT calls the routine END --  EVENTPRV (step 1008) which is described below in connection with FIG. 14. Otherwise, END --  EVENT returns an error to the application layer 12 (step 1009). Finally, END --  EVENT returns a status to the application layer 12 (step 1010). 
     END --  EVENTPRV Service Routine Call 
     END --  EVENTPRV is a service routine called by the routines END --  EVENT and END --  EVENTW as described above. Its purpose is to store data collected by the end event service routines in the facility entries. To do this, END --  EVENTPRV takes the contents of the parameters it receives from the end event service routines, validates them, and copies them into the facility entry. The operation of EVENTPRV is described below in connection with the flow chart of FIG. 14. 
     Referring to FIG. 14, END --  EVENTPRV first enables an error condition handler (step 1100) to respond to any errors in the parameters passed by the end event service routines. Next, END --  EVENTPRV validates the contents of the facility number parameter (step 1102), the contents of the event identification (step 1104), and the contents of the handle (step 1106). END --  EVENTPRV returns an error to the end event service routine for any of these parameters that is invalid (step 1108). Next, END --  EVENTPRV clears the event flags (step 1110), and validates the contents of any optional parameters (step 1112). Next, END --  EVENTPRV locates the facility entry corresponding to the facility code parameter passed by the event service routine (step 1114). If there is no facility entry, END --  EVENTPRV returns an error to the event service routine (step 1116). Otherwise, END --  EVENTPRV determines if the event is to be collected (step 1118), i.e., whether the flag for the event is set. If the event is not to be collected, END --  EVENTPRV returns an error to the event service routine (step 1120). Otherwise, END --  EVENTPRV determines the size of the record needed to hold the collected data (step 1122), allocates the space for that record (step 1124), and timestamps the record (step 1126). Having thus prepared the record, END --  EVENTPRV then copies the contents of the parameters passed by the event service routine into the record (step 1128), writes the record to the data collection file 20 (step 1130), and returns a successful status, i.e., SUCCESS, to the event service routine (step 1132). 
     Facility Definition 
     Each application layer 12 that is instrumented with service routine calls to the registrar process 14 must provide a facility definition which describes the events in the application layer and also the data items for each event. The facility definition is stored in the administration database 16 and accessed by the user via the registrar 14 and the schedule user interface 18 in order to accomplish data collection. A facility definition (shown in block diagram in FIG. 15) includes the name of the facility 30, the identification number of the facility 32, the version number of the facility 34, a list of event definitions 36, a list of data item definitions 38 associated with each event, and a list of class descriptions 40. In the example application layer for the ATM, the defined events 36 are checking an account balance, depositing funds, withdrawing funds (all duration events), and displaying an error message (a point event). The code for each event is instrumented by placing service routine calls at its beginning and its end. The data items 38 are pieces of data associated with each event. By default the items shown in Table 1 above are collected for every event. The user, however, can choose to collect additional application layer specific items or to skip any of the standard items. The structure of a data item is shown in FIG. 16. Each item is defined in part by its data type (see Table 3 below for a list of possible data types), and is further defined by an identifier 50; a size 52, which indicates the maximum size in bytes of the item; a report header 54, which is text used to label the item in a report; a width 56, which indicates the number of spaces in which to display the item in a report; a usage type 58, which can have one of several values, including LEVEL, COUNTER, PERCENT, TEXT, and PRIVATE (see Table 4 below for a list and explanation of usage types); and a characteristic 60, which indicates, for example, whether the item is printable or nonprintable. 
     
                       TABLE 3______________________________________ASCIC      Varying length counted string      of up to 255 bytesASCIW      Varying length counted string      of up to 16383 bytesBYTE       Signed byteFIXED.sub.-- ASCIC      Fixed length counted string of up to 255 bytesLONGWORD   Signed longword (4 bytes)QUADWORD   Signed quadword (8 bytes)WORD       Signed word (2 bytes)______________________________________ 
    
     
                       TABLE 4______________________________________COUNTER   Typically a running count or totalLEVEL     A meter or gauge that indicates the current value     of some metricPERCENT   A percentage, similar to LEVEL, except that     it has upper and lower limitsPRIVATE   Facility-defined data that does not fall into any     other categoryTEXT      Text characters______________________________________ 
    
     Finally, the list of class definitions 40 identifies sets of events definitions 36 and data item definitions, which a user can select as a group in a facility selection described below. 
     Facility Selection 
     A facility selection describes the data for the events and items that each application layer 12 gathers during a collection. The collection tool 10 performs data collection with minimal overhead and performance impact. However, the overhead of course increases as the user selects more and more facilities from which to collect data. For example, in a busy environment, the data collection file 20 becomes very large, which can cause the application layer to quickly use up available disk space. Therefore, the user can choose to limit his collection to a specific function or area of the application layer. To do this, he selects one or more of the classes from the facilities described above. The structure of a facility selection is shown in FIG. 17 and includes a list of facility names of facility definitions 60 from which to collect data on events and items, a comment 62 which describes the purpose of the collection, and a list of options 64 which specify which classes from each facility. 
     Information stored in the administration database becomes a part of a facility selection according the facility selection routine shown in the flow chart of FIG. 18. Inputs to the facility selection process are an item and item group information already in the database, one or more Facility Definitions, a facility identification, a pointer to version number of the facility, a pointer to the group names, and a pointer to list of items. If, in step 1200, the pointer to group name is null, the routine returns an error to the user interface. Otherwise, the routine determines if the length of the group name is valid (step 1202). If so, the routine retrieves the version number and group name (step 1204). 
     Next, the routine performs a number of error checks. If an item name is not defined for the facility (step 1206), the routine returns an error to the user interface (step 1208). Likewise, if an item group name is not defined for the facility (step 1210), the routine returns an error (step 1212). Finally, if the pointer to list of items is null (step 1214), the routine returns an error to the user interface (step 1216). 
     Otherwise, if the error checks do not return errors in steps 1206-1216, the routine retrieves the item list (step 1218) and validates each item in list (step 1220). If any item is a collector item group (step 1222), the routine creates item list entries for each item in group (step 1224). On the other hand, if any item is a collector item (step 1226), e.g., one of the standard resource items, creates an item tuple for the item and includes the tuple in facility definition (step 1228). And if any item is a group name (step 1230), the routine retrieves the item records (step 1232), create entries in the item list (step 1234), and includes a group tuple in facility definition (step 1236). Finally, the routine checks to see if a class option was entered. If so, the routine validates the class name and the existence of the events and any items to be associated with each event. If these exist, then the routine creates a class tuple for the class and event item tuples for the class. Whether or not a class was entered, a default class ALL is created, which contains all of the events and items for all of the events. 
     Schedule Interface 
     In order to collect data from the various applications and application layers running on a system, the user schedules a collection via the schedule user interface 18 (FIG. 2). In the scheduled collection, the user specifies which data to collect, how much data to collect, when to collect the data, and where to store the data. The amount of data collected depends on how many processes on each node of the system are collecting data. The user can select a subset or all of these processes. Each layer in each application that contains service routine calls includes a call to INIT which registers the process and facility information. This information includes the name of the image, the name(s) of the facilities that called INIT, the registration identifier for the process, the process identification number, and the name of the node on which the process is running. The schedule information further includes the name of the output file for the collected data, the start and end times, which facility selection to use, and whether to collect from every node in a computer system, e.g., every node in a VAXcluster, or from a single local node. 
     One routine necessary to export a facility definition to external computer systems is the Facility Extract routine shown in the flow chart of FIG. 19 which inputs a facility definition from the administration database and outputs a file containing a representation of that definition. First, the routine copies the facility version number (step 1300) and creates and opens the extraction file (step 1302). Having created the extraction file, the routine next creates a version record (step 1304) within the file, and writes version record from the database to the file (step 1306). 
     Next, the routine checks the user&#39;s privileges (step 1308). If the user&#39;s privileges are sufficient to meet a predefined standard, the routine attempts to locate the facility definition in the administration database (step 1310). If the facility definition is not found (step 1312), then the routine returns an error (step 1314). Otherwise, if the facility definition is found, the routine again check the user&#39;s privileges (step 1316). If the privileges are not sufficient, the routine returns an error (step 1318). Otherwise, the routine writes the facility main record (step 1320) to the extraction file by processing each facility table and writing the records for each of the item records, item group records, event records, event item records, class records, and default class records to the file (step 1322). 
     Formatting Data Collection File 
     After a scheduled data collection is completed, the data collection file 20 can be merged with previously created data collection files to form a single data file, e.g., a Rdb/VMS database file or a VMS RMS file. Thus, the user can conveniently maintain all of the data for one or more collections. Having formatted the data, the collector can also generate several tabular reports from the formatted data. For example, a Detail Report is useful to application programmers for debugging purposes since it shows the actual values of items for each occurrence of a duration event or point event, the time each event occurred, and other item data. Other reports include a Frequency Report which lists the number of occurrences of each event per second, per minute, or per hour, and a Summary Report which lists different statistics for each item, including maximum, minimum, mean, standard deviation, count (number of occurrences), total, and 95th percentile. 
     The source code for the application event collector (supplied in microfiche form in Appendix A and incorporated herein by reference) embodies the software modules described above. The programming languages used are VAX C version 3.0-031 and VAX BLISS-32 version 4.5-862. The computer used is a VAX 8820 and the operating system used is VAX/VMS 5.2. 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document as it appears in the Patent and Trademark Office files, but otherwise reserves all copyright rights whatsoever. 
     Other embodiments are within the following claims.