ControlFile
Waiting to read or update the pg_control file or create a new WAL file.
Detailed Description
The control file pg_control is an 8kb binary file which stores information about various aspects of the PostgreSQL server's internal state, such as the most recent checkpoint, as well as fundamental parameters set by initdb. It is located in the cluster's global/ directory.
The Write Ahead Log (WAL) is the standard way of ensuring data integrity.
How to reduce this wait
Updating the control file and writing WAL logs are fundamental to the normal operation of the database.
Ensure the server I/O subsystem is performing correctly across the cluster.
Additional Links
PostgreSQL Docs - Wait Events of Type IO
PostgreSQL documentation - Write-Ahead Logging (WAL)
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