Patent Publication Number: US-6910036-B1

Title: Database performance monitoring method and tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of patent application Ser. No. 10/013,410, filed Dec. 11, 2001, abandoned, and claims priority therefrom. 

   STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT 
   None. 
   TECHNICAL FIELD 
   The present invention relates to database performance monitoring. More particularly, the invention relates to a method and tool for monitoring the process performance of a database to obtain the time needed to process requests and statements without tracing the database. 
   BACKGROUND OF THE INVENTION 
   Databases have seen an increase in use over the years. A database is a collection of data that is organized on a computing device so that its contents can easily be accessed, managed, and updated. The most prevalent type of database is a relational database. A relational database is a tabular database in which data is defined so that it can be reorganized and accessed in a number of different ways. Databases contain aggregations of data records or files, such as sales transactions, product catalogs and inventories, and customer profiles. There are at least three key players in the use of these databases; a database administrator or DBA, one or more application developers, and the users within the user community. Typically, a DBA directs or performs all activities related to maintaining a successful database environment. The responsibilities of a DBA include designing, implementing and maintaining the database system; establishing policies and procedures pertaining to the management, security, maintenance and use of the database management system (DBMS) and training employees in database management and use. 
   Developers are charged with developing the application code used by the user community to access and utilize the database. The application code may be written in a variety of languages, such as JAVA, COBAL, or C++. However, the developer will embed Structured Query Language (SQL) within the application code, which is then used to communicate with the database. SQL is a standard interactive user and program interface language for communicating with the database, such as for getting information from the database or for updating the database. SQL queries take the form of a command language that lets the user select, insert, update and find the location of data, among other things. 
   The final key player is the user within the user community. The user may be any of a number of individuals and may access the database for any of a number of reasons. One of the most important aspects of database use to the user is the response time experienced when a request is sent. Thus, one of the major tasks of developers and DBAs is lower the response time as much as possible. Over the last few years, databases have seen an enormous growth in size. This growth adds to the already challenging task of maintaining and increasing the performance of the databases. Developers must craft efficient application codes and DBAs must tune the databases to help meet the required or desired processing windows. Despite the best efforts of the developers and the DBAs, many users remain dissatisfied with the response times experienced in the use of the database. 
   One of the challenges experienced by DBAs is determining the root cause of performance problems that lead to longer response times. In a typical scenario, a user will experience less than desirable response times, and will voice a concern to the DBA or developer. Typically, both the user and the developer initially take the position that the database is the source of the problem. The DBA then faces the challenge of demonstrating to the user and developer that the database may not be the root cause of the performance problem. There are three basic problem areas within the structure of a database system that could be responsible for the performance problem. First, the problem could exist within the database and its management. The database problems could result from unnecessary constraints and bottlenecks. Second, the problem could exist within the network connecting the user to the database. The network problems are largely caused by bottlenecks or limitations of the network bandwidth. Third, the problem could exist within the application code written by the developer. Application code problems typically result from poorly or inefficiently drafted SQL statements. A poorly written SQL statement can be defined as one that consumes many buffers, consumes more disk input/output (i/o) than is necessary or one that runs for a long period of time. Normally, SQL statements that have long execution times are also those that consume many buffers and result in large disk i/o. 
   Thus, it typically falls upon the DBA to determine which of the above three problem areas is responsible for the poor performance. As noted above, by default, the user community typically assumes that the cause of the problem is the database. This reflects poorly on the DBA, especially if the problem is not caused by the database. The DBA can control the database management, but not the application code being used or the network and any problems associated with the network. To understand the source of the performance problems, a DBA needs to know what SQL statements the users are executing, how long each statement runs, and any process bottlenecks experienced. Unfortunately, databases existing on the market today, such as the widely used Oracle database family from Oracle Corporation, do not make this process intuitive or easy. 
   If a user complains to the DBA that a particular job or request was slow in executing, the job is typically already done executing. To better understand the problem, the DBA can ask the user to rerun the job. The DBA can then use existing database tracing tools to trace the run time associated with the job. This tracing process is very accurate, but is burdensome to the database. In other words, the tracing process imposes an additional load on the database by requiring CPU cycles from the server. Moreover, the tracing process generates large trace files that often consume all of the available storage. The tracing process also consumes the time of the DBA in administering the trace and in analyzing the trace results. Because of the above noted problems, it is not practical or operationally possible to capture database-wide performance data on more than an ad-hoc basis. DBAs must use the tracing process sparingly, and thus have only a limited operational knowledge about the performance of the database, which can translate into poor user customer service. 
   Currently, there is no available method or tool that can be used by DBAs to monitor the process performance of the database that does not impose a large amount of overhead on the database system and the resources of the DBA. It would be desirable to provide a method and tool for obtaining process performance data about the database and its use without imposing additional overhead on the database. It would also be desirable to provide process performance data in a manageable form that can be quickly analyzed to ascertain information about the run time of each SQL statement issued to the database. 
   SUMMARY OF THE INVENTION 
   The present invention provides a method and system for use with database administration. More specifically, the present invention provides a method and system for monitoring the process performance of a database that accepts and records SQL statements and that records the status of a session of use of the database. The invention obtains the SQL address and hash value for each SQL statement, the current session status corresponding to each SQL statement and the previous session status corresponding to each SQL statement. The invention also records a time stamp at the time the session status information is obtained. The information gathering steps are repeated at a predetermined interval of time. Using the information gathered, the run time for each SQL statement is calculated. The run time for each SQL statement may then be reviewed to determine which SQL statements experience the greatest run time, which allows DBAs to locate the source of any performance problems. The invention includes generating reports containing the calculated run times that are easily reviewed by the DBA. 
   Additional advantages and novel features will be set forth in the description which follows and in part may become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The present invention is described in detail below with reference to the attached drawing figures, wherein: 
       FIG. 1  is a schematic diagram of an overall system suitable for use in implementing the present invention; and 
       FIG. 2  is a flow chart illustrative of one embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention provides a system and method that provides DBAs an opportunity to monitor the process performance experienced by users of the database without imposing an unnecessary burden on the database. The invention combines information retained by the database to obtain approximate run times associated with identified SQL statements. A report is generated at a desired frequency which is easily analyzed to determine the root cause of any performance problems. Through use of the present invention, the performance of the database system can be enhanced on a proactive basis without the need to wait for users to complain about particular problem areas. 
   The basic system used in connection with the present invention is shown in FIG.  1 . As seen in  FIG. 1 , a database  10  is provided. Database  10  contains, among other things, a user process pool  12  and a statement pool  14 , further details of which are described more fully below. Database  10  may be accessed by a number of users  16  through one or more applications  18 . Users  16  can be any of a variety of people that access and use database  10  for a variety of reasons. For example, an officer of a company may wish to utilize database  10  to acquire financial data regarding the company over a period of time. Alternatively, a marketing representative of a company may wish to utilize database  10  to acquire sales information. The uses of database  10  are virtually limitless. Users  16  communicate with database  10  through applications  18 . Applications  18  are typically provided by developers within the company utilizing database  10 , such as an information services or IS group within the company. The applications  18  can be written in java, C++, COBAL or other languages. However, SQL is imbedded within the application code, which allows communication with database  10 . Database  10  understands the SQL statements and communicates any requested information back to the user  16 . The communication between database  10  and users  16  takes place across a network  20 . 
   As mentioned above, database  10  is typically capable of performing a trace of the activities taking place on the database. Typically, if a user  16  complains to the DBA about a slow response time experienced in using database  10 , the DBA can request the user to rerun the particular job at issue, and then activate the tracing feature of the database  10 . The tracing feature produces a trace log file  22 , which is stored on disk. The trace log  22  could be used by the DBA to determine the cause of the performance problems experienced by user  16 . However, the trace log file  22  is very large, usually on the order of hundreds of megabytes per trace. Because the file  22  is so large, it is difficult to analyze in a time efficient manner. Finally, because the trace log is generated by the database  10 , the generation of the trace log  22  requires valuable system resources and CPU time. For all of these reasons, it is not operationally possible to utilize the tracing feature of database  10  on a continual basis. 
   The invention provides an observation tool  24  to address the above noted deficiencies with trace log file  22 . Observation tool  24  communicates with database  10  to observe the process performance experienced by users  16  in their interaction with database  10 . Observation tool  24  can be used to continually monitor the database  10  and can produce a report that is more easily analyzed by a DBA than the trace log file  22 . The report generated is much smaller than the trace log file  22  and therefore consumes far less disk space than the trace log file  22 . The methodology used by observation tool  24  is discussed in detail with reference to FIG.  2 . Prior to the discussion of  FIG. 2 , further details of database  10 , user process pool  12  and statement pool  14  will be described. 
   Database  10  is a relational database that is in common use today. As an example, the invention is particularly suited for use with an Oracle Corporation database. The database accepts SQL statements for processing from the users  16  through applications  18 . Within the database  10  are the user process pool  12  and the SQL statement pool  14 . User process pool  12  collects and stores a variety of information about the users  16 . User process pool  12  stores the username for the user  16 , the login time, the status of the process, the SQL hash value and SQL address, the previous SQL hash value and the previous SQL address. The status of the process is either active or inactive. An active process is one for which a SQL statement has been received by the database  10  that the database  10  is still working on. In other words, an active process in one that has not yet been completed. The SQL hash value and SQL address map to a corresponding SQL hash value and SQL address within the SQL statement pool  14 . The SQL hash value and SQL address indicate the current SQL statement that is being processed by the database  10  for the particular user  16 . The previous SQL hash value and the previous SQL address indicate the immediately preceding SQL statement that was processed by the database  10  for the particular user  16 . Importantly, the user process pool  12  does not contain any run time information regarding the SQL statements being processed. The database  10  thus tracks the SQL statements being submitted but does not track the run time associated with each SQL statement. SQL statement pool  14  contains, among other things, unique SQL hash values and SQL addresses that correspond to SQL statements. In addition, the SQL statement pool  14  may contain information regarding memory usage and disc usage. Therefore, the pools  12  and  14  provide a history of all of the queries and the resources they have consumed, but do not provide any information regarding the time consumed by the queries. 
   When a user  16  logs into the database  10 , the user name and login time are recorded in user pool  12 . When the user  16  submits a statement or request to the database  10 , the status of the process becomes active. In addition, the SQL hash value and address are recorded. For example, suppose User 1  submits Query 1  to the database. User 1  is recorded in the user pool  12  and Query 1  is recorded in the statement pool  14 . As soon as the user hits enter, the status of the process is updated to active within user pool  12  because the SQL query is now being processed by the database  10 . This information is used by observation tool  24  to generate a report for the DBA regarding the process performance experienced by users  16 . In other words, observation tool  24  tracks and records the run time experienced by each user for the particular SQL statements being submitted. 
   The methodology used by observation tool  24  is best understood with reference to FIG.  2 . Broadly, the invention monitors the status of the session and the SQL statement for the session. If the status is active, the invention looks to see what SQL statement is currently being processed and tracks how long, utilizing an accounting process, the SQL statement requires for processing. 
   The methodology begins by recording a time stamp, as shown at  26  in FIG.  2 . The time stamp is used as a reference so that the status of the session and the address and hash value of the SQL statements at a specific point in time are known. The process continues by obtaining the address and hash value of the SQL statements for a particular user, as shown at  28 . The session status is also obtained, as shown at  30 . The session status reflects whether the database  10  is still processing the SQL statement and is active, or is done processing the SQL statement and is inactive. A number of different scenarios are accounted for in the remaining process of FIG.  2 . The scenarios depend on whether the address and hash value are new or old, whether the session status is active or inactive, and whether the previous session status is active or inactive. The first step in determining which of the scenarios is taking place is to determine whether the address and hash value obtained in step  28  are new or old, as shown by  32 . 
   If the address and hash value are new, it means that a new SQL statement is being processed by database  10  that has not previously been processed for that particular session. If the address and hash value are new, the process continues by determining whether the status of the session is active or inactive, as shown at  34 . If the status of the session is active, it means that the database  10  is still processing the new SQL statement. As such, the time needed to process the SQL statement needs to be accounted for. To that end, a time charge is noted and added to the time required by this particular SQL statement, as shown at  36 . 
   In a preferred embodiment, the process of  FIG. 2  is executed on a regular incremental time basis, such as every ten minutes. The time interval can be decreased or increased depending on the accuracy needs of the DBA. For example, by reducing the time interval, the accuracy of the information obtained increases. As noted at step  36 , a partial time increment is added to the time charge for the SQL statement. In a preferred embodiment, the time charge added at step  36  is twenty-five percent of the given time increment. In other words, if the time interval being used in the process of  FIG. 2  is set to ten minutes, the scenario ending at step  36  would result in a charge of 2.5 minutes being added to the record for the particular SQL statement being executed by a particular user  16 . 
   If the status is determined to be inactive at step  34 , then no charge is added to the record for the new SQL statement, as shown at  38 . This scenario reflects the case where a new SQL statement is experienced by the session, but which has been processed by the database  10  within the time interval that has been set. In other words, if the time interval is ten minutes, the new SQL statement is received and executed by database  10  within the ten minute interval. Because the SQL statement is executed within the interval, no charge is recorded for the SQL statement. 
   Returning to step  32 , if the SQL address and hash value obtained for the user are determined to be old, the process continues at step  40  by checking the previous session status. As shown at  42 , the process determines whether the previous session status was active. This information is used along with the current session status. Therefore, if the previous session status was active, the current session status is determined, as shown at  44 . If the current session status is active, a time charge is added to the record for this SQL statement and user as shown at  46 . Because the previous session status was active and the current session status is active, the database  10  was processing the SQL statement for the full interval. Thus, the full time interval is added to the time charge in this instance. If the time interval is ten minutes, then a ten minute time charge is added to the record for the SQL statement. Returning to step  44 , if the current session status is determined to be inactive, a partial interval time charge is added to the record for the SQL statement and user, as shown at  48 . The session status is also reset to inactive, as shown at  50 . This scenario applies to a situation where the SQL statement was being processed by the session in the previous time interval, but processing was completed sometime during the current time interval. Thus, only a partial-interval time charge is added to the record for the SQL statement since the database  10  is not processing the SQL statement for the full time interval. As an example, half of the time interval can be added to the time record for the SQL statement. If the time interval is ten minutes, a five minute time charge can be added to the time record for the SQL statement. 
   Returning to step  42 , if the previous session status is determined to be inactive, the current session status is determined at  52 . If the current session status is active, a partial time charge is added to the record for the SQL statement as shown at  54 . This scenario addresses the situation where the SQL statement has been seen before by the session, the previous session status was inactive, but the current session status is active. Because the database  10  is not processing the SQL statement for the full length of the interval, only a partial time charge is added, and the session status is reset to active as shown at  56 . As an example, if the time interval is ten minutes, a partial time charge of half the interval, or five minutes, can be added to the time charge for the SQL statement. If, however, the current session status is determined to be inactive in step  52 , no charge is added to the time record, as shown at  58 . This reflects the scenario where the SQL statement is old for the session, but the previous and current session status are inactive. In this scenario, the SQL statement is merely waiting to be aged out of the least recently used (LRU) list. 
   After steps  36 ,  38 ,  46 ,  50 ,  56  and  58 , the process waits the predetermined time interval and returns to step  26  to record the current time stamp. If the time interval is ten minutes, the process described above with reference to  FIG. 2  takes place every ten minutes. Time charges are recorded for each SQL statement along with the user issuing the SQL statement. Returning to  FIG. 1 , when, a user  16  submits a query to database  10  through application  18 , observation tool  24  operates as described with reference to  FIG. 2  to monitor the session. Each SQL statement in the session is tracked and a run time for the statement is recorded. The process of  FIG. 2  is used to total the run time for each SQL statement. It should also be understood that certain sessions are not activated by a user  16 , but are scheduled queries that run on a regular basis. These sessions may be known as batch jobs and the invention applies equally to the execution of batch jobs as well. 
   The invention thus gathers a time stamp, a user identification such as the username, the SQL address and hash value and the session status information. This information is used to calculate the run time for each SQL statement received by database  10 . Using this information, the DBA can demonstrate to developers and the user community the source of the performance problems. The SQL statements having long run times can be identified, and the application code associated with the SQL statements can be revised to improve the efficiency of the code. 
   The invention can be used to generate a report that is useful to the DBA on a regular basis. The report will preferably contain the user name, the SQL address, the SQL hash value, the SQL statement text and the execution time of the SQL statement calculated as described above with reference to FIG.  2 . It can therefore be seen that the present invention can be used to extract SQL statements from the database  10  and determine the run time associated with each SQL statement, without imposing the overhead required by tracing the database. The invention provides the user community a better level of customer service and allows the DBA to focus tuning efforts on long-running application statements. 
   Alternative embodiments of the present invention become apparent to those skilled in the art to which it pertains upon review of the specification, including the drawing figures. The various computer systems and components shown in FIG.  1  and described in the specification are merely exemplary of those suitable for use in connection with the present invention. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description.