Tracking MAP Usage

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Data Virtualization Manager now allows users to track the usage of virtual tables and virtual views to analyze how frequently they are accessed. This usage data can help users identify and remove unused objects, thereby optimizing resource utilization. As part of the server’s monitoring capabilities, the SQL engine logs the usage count of MAPs - excluding metadata calls - into SMF records. This logging helps users identify MAPs that are consuming the server memory but are not actively used.

The usage count is updated in the SMF subtype 21 (see Record Subtype 21: Tracking SMF Record) each time a MAP is queried. This record includes the following details:

  • The name of the MAP

  • The date and time of the query

  • The schema under which the map is defined

  • The usage count of the MAP

This information is saved in the SMF record when the server shuts down. By analysing these records, users can identify MAPs that are consuming server memory without being actively used. This allows them to remove unused MAPs and retain frequently accessed ones, thereby optimizing memory usage and improving server performance.

To enable MAP usage tracking, you need to set the following parameters to Yes in the PRODDMF parameter group:

Table 1. Parameters for tracking MAP usage
Parameter name Parameter description Default Value Update Output only
DMFMAPUSAGENZERO

WRITE NON-ZERO USAGE DMF MAP SMF RECORDS

This parameter records the map details with non-zero usage counts.

DMF Maps supports the following MAP types: ADABAS, SEQUENTIAL, VSAM, NATURAL, DB2, JGATE/DRDA, IMS, SQL VIEWS, and BROKER, both in the default schema (DVSQL) and any user-defined schema on the server.		 NO YES NO
DMFMAPUSAGEZERO

WRITE ZERO USAGE DMF MAP SMF RECORDS

This parameter records map details with a usage count of zero.

DMF Maps supports the following MAP types: ADABAS, SEQUENTIAL, VSAM, NATURAL, DB2, JGATE/DRDA, IMS, SQL VIEWS, and BROKER, both in the default schema (DVSQL) and any user-defined schema on the server.		 NO YES NO

For more details about the PRODDMF parameter group parameters, see PRODDMF parameter group.