GS_WLM_INSTANCE_HISTORY

The GS_WLM_INSTANCE_HISTORY system catalog stores information about resource usage related to CN or DN instances. Each record in the system table indicates the resource usage of an instance at a specific time point, including the memory, number of CPU cores, disk I/O, physical I/O of the process, and logical I/O of the process.

**Table 1** **GS_WLM_INSTANCE_HISTORY** column
Column	Type	Description
instancename	Text	Instance name
Timestamp	Timestamp with time zone	Timestamp
used_cpu	Int	CPU usage of an instance
free_mem	Int	Unused memory of an instance (unit: MB)
used_mem	Int	Used memory of an instance (unit: MB)
io_await	Real	Specifies the io_wait value (average value within 10 seconds) of the disk used by an instance.
io_util	Real	Specifies the io_util value (average value within 10 seconds) of the disk used by an instance.
disk_read	Real	Specifies the disk read rate (average value within 10 seconds) of an instance (unit: KB/s).
disk_write	Real	The disk write rate (average value within 10 seconds) of an instance (unit: KB/s).
process_read	Bigint	Specifies the read rate (excluding the number of bytes read from the disk pagecache) of the corresponding instance process that reads data from a disk. (Unit: KB/s)
process_write	Bigint	Specifies the write rate (excluding the number of bytes written to the disk pagecache) of the corresponding instance process that writes data to a disk within 10 seconds. (Unit: KB/s)
logical_read	Bigint	CN instance: N/A DN instance: Specifies the logical read byte rate of the instance in the statistical interval (10 seconds). (Unit: KB/s)
logical_write	Bigint	CN instance: N/A DN instance: Specifies the logical write byte rate of the instance within the statistical interval (10 seconds). (Unit: KB/s)
read_counts	Bigint	CN instance: N/A DN instance: Specifies the total number of logical read operations of the instance in the statistical interval (10 seconds).
write_counts	Bigint	CN instance: N/A DN instance: Specifies the total number of logical write operations of the instance in the statistical interval (10 seconds).