DCOLLECT - Data Collector

Enhanced Definition

`DCOLLECT` (Data Collector) is an IBM utility within `DFSMS` (Data Facility Storage Management Subsystem) used to gather comprehensive information about data sets, volumes, `SMS` constructs, and `HSM` (Hierarchical Storage Manager) managed data on a z/OS system. It collects this metadata and writes it into a sequential data set (or `VSAM KSDS`) for subsequent analysis, reporting, and storage management tasks. Its primary purpose is to provide a detailed inventory of storage resources. DCOLLECT is an IBM z/OS utility that collects comprehensive information about data sets, volumes, storage groups, and other storage-related entities on a z/OS system. It generates a VSAM Key -Sequenced Data Set (KSDS) containing various record types that describe the collected storage attributes. Its primary purpose is to provide a snapshot of the storage environment for analysis, reporting, and management.

Key Characteristics

- Comprehensive Data Collection: Gathers detailed attributes for VSAM and non-VSAM data sets, volumes, storage groups, data classes, management classes, storage classes, pools, and HSM migration/backup information.
- Structured Output Records: Produces fixed-length records in a predefined format (e.g., DCR for data set records, DCV for volume records, DCS for storage group records), which can be easily processed by other programs.
- Batch Execution: Runs as a standard z/OS batch job, typically invoked via JCL, allowing for scheduled and automated execution.
- Configurable Scope: Can be configured to collect data for specific volumes, storage groups, data set name masks, or the entire system, providing flexibility for targeted analysis.
- Input for Other Utilities: The DCOLLECT output often serves as input for other DFSMS utilities (like DFSMSdss for data movement) or custom reporting applications.
- Direct Data Access: Retrieves information directly from VTOCs (Volume Table of Contents), VVDSs (VSAM Volume Data Sets), SMS control data sets (CDSs), and HSM control data sets.

Use Cases

- Storage Reporting and Capacity Planning: Generate detailed reports on data set allocation, free space, utilization trends, and SMS compliance to aid in capacity planning and chargeback accounting.
- Auditing and Compliance: Verify SMS policy enforcement, identify non-compliant data sets, or track data set attributes for security audits and regulatory requirements.
- Problem Determination and Optimization: Analyze data set characteristics (e.g., extent usage, fragmentation) to troubleshoot storage-related performance issues or identify candidates for reorganization or migration.
- Migration and Consolidation Projects: Gather accurate inventory data of existing storage resources before migrating data to new storage subsystems or consolidating storage pools.
- Input for Custom Applications: The DCOLLECT output can be processed by REXX, COBOL, SAS, or other programming languages to create highly customized reports and dashboards.

Related Concepts

DCOLLECT is a fundamental component of DFSMS, providing the raw data necessary for effective storage management. It works in conjunction with SMS by collecting detailed information about SMS-managed and non-SMS-managed data sets, storage groups, and classes, enabling administrators to verify and report on SMS policies. Its output is often used by HSM to track migrated and backed-up data, and by DFSMSrmm for tape library management. The utility is typically invoked through JCL, with its output frequently processed by custom programs for advanced analysis.

Best Practices:

Scope Appropriately: Use VOLUME, STORGRP, or DSNAME filters to limit the scope of DCOLLECT runs, especially for frequent executions, to minimize system resource consumption.
Schedule Off-Peak Hours: Perform full system DCOLLECT runs during periods of low system activity to prevent performance impacts on critical online transactions or batch workloads.
Automate Processing: Integrate DCOLLECT into automated JCL streams that subsequently process the output using REXX, COBOL, or SAS programs to generate reports and trigger alerts.
Retain Historical Data: