Application Performance for DB2

Wayne Slomiany

January 29, 2008

2

Agenda

• Targeted DB2 Data for Testing • Efficient Coding Practices • Efficient Application Relationships • Using DB2 Stored Procedures • Resolving DB2 Abends • External Influences

3

Targeted DB2 Data for Testing

Testing Audit Reports

z/OS Distributed

Subset Extract

Apply Privacy Rules Privacy Audit Reports

Load Maintain Integrity

z/OS Distributed

Less Data, Less Resources

4 • Large TABLE loads can cause excessive resource usage and long LOAD times.

• Optimization of data used will decrease this.

• Usage of tools that support SORTKEYS in the load process which bypasses INDEX Key validation on each KEY written.

• Specifying LOG NO will prevent logging.

5

Relationships of Data Intact

• Referential Integrity • Application Relationships

Data Relationships

Production Distributed Subset Extract

6

z/OS Relationships

Production AR/RI z/OS

7

8

Efficient Coding Practices

“The later performance problems are caught in the life cycle, the more costly they are to fix. Inefficiencies introduced in design can cost twice as much to fix during programming, four times more during system testing, and eight times more when the application enters production.”

Accenture

9

Pro-Active Application Relationship Management

• Normalize Database Including Application Relationships during Logical Design Phase − Those used in Programs − Those used in Driving Files • Perform Physical Design (Table and Index) de-Normalizing for Performance

Pro-Active Application Relationship Management

• Table joins tend to cause de-Normalization to improve performance.

• Focus on proper creation of INDEXs.

• Make Only Acceptable Relationships Available to Applications.

10

Create a Baseline of the Application

• Identify what is acceptable (SLAs) for a particular application.

− End User response times.

− Overall system performance.

− Overall resource usage.

• Use this to compare future releases and Production.

− Identify problem areas.

− Identify any changes made.

11

Benefits of DB2 Stored Procedures

12 • • • •

Reduce Network traffic Improve Security Called from many programs/platforms Easier to maintain data & logic Browser Middleware S390 Servers CICS/ IMS Batch Data Servers

DB2 Stored Procedures

• They reduce the SQL statements needed in the calling program.

• SQL is executed by the stored procedure and results are returned to the calling program.

• They have separate authority from the caller, allowing them to access and update tables that the caller can’t.

13

DB2 Stored Procedures

• The caller only needs authorization to execute the stored procedure.

• This provides an additional level of security by preventing corruption of the SQL.

• This also eliminates outdated Client processes, the current stored procedure is always executed. 14

DB2 Stored Procedures

• They must run using Language Environment.

• If a stored procedure does abend, there is only the LE dump to work with.

• The programmer could add his own trace code to try to narrow down the cause of the abend. 15

DB2 Stored Procedures Challenges

Analysis Debugging Testing Production Support

- PLUS -

Added Complexity Programmer Familiarity Project Deadlines Prevent Problems Customer Satisfaction Realize Benefits

16

XPEDITER for DB2 Stored Procedures

-------------------- XPEDITER/TSO - Process DB2 Store Procedures ------------- COMMAND ===> Primary Commands: SEtup (display setup menu) Stored Procedure Name ===> DOE.SPTEST1

Load Module name ===> PGM12345 (optional) Client End User Name ===> JOHNDOE DB2 AuthID ===> (DB2 Version 5 only) Luname ===> (DB2 Version 5 only) DB2 Sub System Name ===> DB61TEST Maximum number of Tests ===> (1 - 9999) Specify Execute Jcl ===> N Jobcard Information: ===> //PFHRAS0 JOB (#ACCONT),CLASS=A,MSGCLASS=X, ===> // MSGLEVEL=(1,1) (Y or N) Press ENTER to process or enter END command to terminate 17

XPEDITER for DB2 Stored Procedures

---------------------- XPEDITER/TSO - SELECT JOB STEP ----- Row 1 to 1 of 1 COMMAND ===> SCROLL ===> PAGE Line Commands: Primary Commands: I - Interactive testing Edit - Display converted selected steps U - Unattended testing END - Exit without processing IC UC - Interactive Code Coverage - Unattended Code Coverage RUN SEtup - Submit and connect - Setup work datasets SUBmit - Convert selected steps and submit blank - Reset I/U/C STatus - Display status of submitted job(s) Dataset: 'SYS1.PROCLIB(D61WLM2)' PROGRAM INITSCR STEPNAME PROCNAME PROCSTEP EXEC PGM ------------------------- ------------------------------------------------- __ PGM12345 ________ XPTS0 XPAE001 RUNPROG XPTSO ******************************* Bottom of data ******************************** 18

XPEDITER for DB2 Stored Procedures

------------------------- XPEDITER/TSO - SOURCE ----------------------------- COMMAND ===> SCROLL ===> CSR BEFORE BREAKPOINT ENCOUNTERED ** END ** 19 ----- -------------------------------------------------- Before PGM12345 <> =====> B FUNCTION = 'COMMAND'; /* SET FUNCTION FOR IFI CALL */ 000265 IFCA.LNGTH = STORAGE(IFCA); /* BYTES USED IN MEMORY */ 000266 000267 000268 IFCA.EYE_CATCHER = 'IFCA'; /* EYE CATCHER */ IFCA.OWNER_ID = 'LOC2'; /* DB2 LOCATION 1=LOCAL, 2=REMOTE*/ FREE RETURN_AREA; /* FREE STORAGE AND THEN */ 000269 000270 000271 000272 000273 000274 000275 000276 000277 000278 000279 /* ALLOCATE STORAGE FOR THE */ ALLOCATE 1 RETURN_AREA, /* RETURN AREA */ 2 LNGTH, 2 RTRN_BUFF CHAR(4096); RTRN_BUFF = ' '; /* CLEAR THE RETURN BUFFER */ RETURN_AREA.LNGTH = 4096; /* LENGTH OF RETURN BUFFER */ TEXT_OR_COMMAND=BLANK; /* CLEAR THE DB2 COMMAND AREA*/ OUTPUT_AREA.UNUSED = '00000000'B; /* CLEAR THE UNUSED AREA */ OUTPUT_AREA.LNGTH = LENGTH(INPUTCMD)+4; /* GET REAL LENGTH OF */ OUTPUT_AREA.TEXT_OR_COMMAND = INPUTCMD; /* ACTUAL DB2 COMMAND */

Resolving DB2 Application Abends

• Abends, including DB2, can use a large portion of the processor.

• Resolving them in a quick and complete fashion is important.

• Correlation of Application and DB2 information is important in resolution.

20

CICS Application Abend

• • • • • • • • Locate the task interface element (TIE) for “DSNCSQL”.

Locate the CICS Life of Task (CLOT) in the TIE for DSNCSQL. Locate the SQL-PLIST using the pointer (CLOTPARM) from the CLOT.

Validate the SQL-PLIST by locating the DBRM name once the SQL-PLIST is verified, the statement number, type, APARM (INPUT Host Variables) address, VPARM (OUTPUT Host variables) address, timestamp and pointer to the SQLCA have been located. To locate the SQLCODE, use the SQLCA pointer from the SQL-PLIST. Once located, the SQLCODE must be converted from HEX to DECIMAL before it can be used. For example, A 302 displays as “FFFFFED2” in the SQLCA.

Look up the SQLCODE in the DB2 message and codes manual. The message text does not offer much more than an explanation. There are seldom any suggestions as to the cause of the problem. The statement number is used to locate the SQL statement in the precompile listing.

21

22 Using Correlation

23

24

25

Application Management Solution

Reduce excessive resource consumption at the root cause through a proactive and systemic approach.

26

Application Resource Management provides empirical data to help you make educated decisions.

External Influences

Server Performance Delivery Stats Web Servers Application Servers Database Servers

End user monitoring

Database Utilization J2EE and .NET Analyzer Top App by Traffic

Service Dashboard

Top Server Traffic WAN Utilization Response Times Performance Overview

27

Distributed MQ Application

Client

Query

1. Web application was occasionally failing.

2. Became aware of problem in real time (without any user interaction). Also got background information: unexpected 2033.

Pdaaggr.exe

Answer

N-Tier Server

Request 1 Reply 1

3. Traced the MQ message flow and saw that the 2033 was due to sluggish response from the mainframe application.

Request3 Reply 2 Request 4 Reply 3 Reply 4

Back end Server 4. Analyzed the performance of the mainframe application – and saw a significant issue with MQ system level tracing during bursts of activity.

Pdarep2 28

MQ Performance Impact

• Excessive wait time can impact DB2 performance.

• Difficult to identify the culprit. 29

Environment Tuning • • • Evolving applications introduce more potential points of failure Environmental complexity contributes to resource growth Gradual MIPS consumption can go undetected • Reactive, fire-fighting mindset • Limited expertise and skills • Mainframe costs (hardware and software) are driven by MIPS 30

Dynamic SQL Queries

• Usually rarely used however has great impact.

• Can involve large table scans with long wait times at the user end.

• Minimize and control as best possible.

31

DB2 Environment Considerations

• Manage BUFFER POOLS based on recommendations per Version of DB2.

• Proper BUFFER POOL sizes: a good indicator is ratio of GETPAGES to synchronous reads of no greater than 10:1.

• There is a difference between read-only and read/write tables (maybe a separate BUFFER POOL here).

32

Current Application Performance Metrics 33