Selecting an access method

See Database-processing for additional information about selecting an appropriate access method.

The following keywords allow you to control the input access methods:

• DBACC
• MINCYL

Procedures

Perform the following steps to identify an access method. Different types of input data sets use different keywords.

1. Input image copy and change accumulation data sets

   The utility automatically uses the SAM-E access method for reading an image copy or change accumulation data set. This method provides equal or better performance as compared to previously used access methods and is supported for tape and DASD data sets.

   In previous versions of the utility, the DSACC keyword was used to control the access method. This keyword is still accepted if it is specified with a valid value on a control statement or in an options module, but its value is ignored.

2. Input data set group or area

   Specify the DBACC keyword on a valid control statement or in an options module. Database-processing.

   If you select DBACC(3), you can use the MINCYL keyword to specify a minimum database size in cylinders to be processed with the start I/O access method.

   If the database is smaller than the value you specify, rather than using the start I/O access method, the utility uses EXCP processing, as requested with DBACC(2), for OSAM data sets and VSAM processing, as requested with DBACC(1), for ESDS. Specify the MINCYL keyword on a valid control statement or in an options module.

Example

In the following example, use the start I/O access method for the input data set group. The start I/O access method is used for databases with a minimum of 20 cylinders.