GS_WLM_INSTANCE_HISTORY

GS_WLM_INSTANCE_HISTORY stores information about resource usage related to CNs or DNs. Each record in this system catalog indicates 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. This system catalog can be queried by users with the sysadmin permission only in Postgres.

**Table 1** GS_WLM_INSTANCE_HISTORY columns
Name	Type	Description
instancename	text	Instance name
timestamp	timestamp with time zone	Timestamp
used_cpu	integer	CPU usage of the instance
free_mem	integer	Unused memory of the instance, in MB
used_mem	integer	Used memory of the instance, in MB
io_await	real	Average wait time for an I/O operation on the disk used by the instance. The average value is within 10 seconds.
io_util	real	io_util value of the disk used by the instance. The average value is within 10 seconds.
disk_read	real	Disk read rate of the instance, in KB/s. The average value is within 10 seconds.
disk_write	real	Disk write rate of the instance, in KB/s. The average value is within 10 seconds.
process_read	bigint	Read rate (excluding the number of bytes read from the disk pagecache) of the corresponding instance process that reads data from a disk within 10 seconds, in KB/s
process_write	bigint	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, in KB/s
logical_read	bigint	CN: N/A DN: logical read byte rate of the instance within the statistical interval (10 seconds), in KB/s
logical_write	bigint	CN: N/A DN: logical write byte rate of the instance within the statistical interval (10 seconds), in KB/s
read_counts	bigint	CN: N/A DN: total number of logical read operations of the instance within the statistical interval (10 seconds)
write_counts	bigint	CN: N/A DN: total number of logical write operations of the instance within the statistical interval (10 seconds)