Retaining Monitoring Information
When you query a Vertica system table, you can get information about currently running queries, the state of various components, and other run-time information. During query execution, Vertica examines the current state of the system and returns information in the result set.
Vertica also provides a utility called the Data Collector (DC), which collects and retains history of important system activities and records essential performance and resource utilization counters.
Data Collector extends system table functionality by:
- Providing a framework for recording events
- Making the information available in system tables
- Requiring few configuration parameter tweaks
- Having negligible impact on performance
You can use the information the Data Collector retains to query the past state of system tables and extract aggregate information, as well as do the following:
- See what actions users have taken
- Locate performance bottlenecks
- Identify potential improvements to Vertica configuration
DC does not collect data for nodes that are down, so no historical data would be available for that node.
Data Collector works in conjunction with Workload Analyzer, a tool that intelligently monitors the performance of SQL queries and workloads, and recommends tuning actions based on observations of the actual workload history.
Where Is DC Information retained?
Collected data is stored on disk in the
DataCollector directory under the Vertica /catalog path. This directory also contains instructions on how to load the monitoring data into another Vertica database. See Working with Data Collection Logs for details.
DC retains the data it gathers based on retention policies, which a superuser can configure. See Configuring Data Retention Policies.
Data Collector tables (prefixed by
dc_) reside in the
V_INTERNAL schema and are provided for informational purposes only. They are provided as-is and are subject to removal or change without notice. If you use Data Collector tables in scripts or monitoring tools, you might need to change your scripts and tools after a Vertica upgrade. Vertica recommends that you use the Workload Analyzer instead of accessing Data Collector tables directly.