Working with Data Optimizer

By using a variety of I/O optimization techniques, the number of accesses to disk and unnecessary wait times are reduced, or eliminated, reducing elapsed run times. Data Optimizer automatically tunes your system to achieve optimum application performance.

Features of Data Optimizer

Data Optimizer provides the following features:

• Robust tuning techniques

  Data Optimizer provides a variety of sophisticated tuning techniques that provide the best possible performance benefits for each type of processing and file structure. Techniques range from simple buffer value changes to more advanced techniques such as dynamically caching buffers, overlapping I/O, building and using LSR pools, and complete rebuilding of channel programs.

• Dynamic tuning based on resource availability

  When a data set that is being opened has been selected for optimization, Data Optimizer checks the availability of a variety of system resources. This check ensures that system capacity is available and that optimal tuning values are selected.

• Dynamic region adjustment

  Data Optimizer can dynamically modify the region values in an address space to compensate for any additional I/O-related storage areas that have been obtained on behalf of an application. This feature eliminates the need to increase the region value on the JOB or EXEC JCL statements to prevent out of storage conditions such as S878 or S80A abends. This feature also prevents the application from seeing a decrease in the amount of available private storage when optimization is used.

• Flexible implementation

  Data Optimizer provides a variety of methods for defining what is eligible for optimization benefits. The MAINVIEW Batch Optimizer dialog allows the creation of a data policy that provides a robust set of selection criteria including JOBNAME, DSNAME, SMSCLASS, and IBM RACF associations. In addition, JCL DD override statements are provided for testing and impromptu optimization specifications at the job step or DD statement level. A User Control exit interface is provided for users that have selection algorithms that are too complex to be accomplished with the data policy.

• Detailed informational messages and statistics reports

  Data Optimizer provides messages that indicate when optimization has been performed. Data Optimizer also indicates the source that requested optimization or exclusion and provides specific reasons when optimization is bypassed for special circumstances. Data Optimizer provides detailed statistics reports that indicate information about the kind of processing that was performed and the amount of savings that was achieved. Job name, step name, ddname, and dsname information that is related to the data set being processed is also provided.

Benefits of Data Optimizer

Data Optimizer provides the following benefits:

• Larger data transfers per I/O operation

  Data Optimizer increases the amount of data movement per I/O request (when appropriate). The increased data movement decreases the number of I/O requests and reduces the elapsed time that is attributed to I/O.

• Improved I/O efficiency

  Data Optimizer learns and records an application’s data access patterns and restructures I/O requests to take advantage of this information. It restructures the requests by using advanced I/O improvement techniques, which include improved buffering, overlapping I/O requests, and decreasing I/O path lengths.

• Reduced elapsed times

  Because Data Optimizer reduces the number of accesses to disk, it reduces or eliminates unnecessary wait times and significantly reduces the number of EXCPs. It automatically performs tuning to maintain optimum application performance without overusing system resources and negatively affecting overall system performance.

• Improved buffering and caching

  Data Optimizer automatically determines and sets the optimum buffering values for the utility or application. As I/O access patterns change for the utility or application, Data Optimizer adjusts these values.

• Virtual storage constraint relief

  Data Optimizer moves data areas above the 16 MB line whenever possible to maximize virtual storage constraint relief for VSAM and non-VSAM processing.

This section provides the following topics:

• VSAM optimization
• Non-VSAM optimization