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22.5.10.32 The ndbinfo pgman_time_track_stats Table

This table provides information regarding the latency of disk operations for NDB Cluster Disk Data tablespaces.

The following table provides information about the columns in the pgman_time_track_stats table. For each column, the table shows the name, data type, and a brief description. Additional information can be found in the notes following the table.

Table 22.322 Columns of the pgman_time_track_stats table

Column Name Type Description
node_id integer Unique node ID of this node in the cluster
block_number integer Block number (from blocks table)
block_instance integer Block instance number
upper_bound integer Upper bound
page_reads integer Page read latency (ms)
page_writes integer Page write latency (ms)
log_waits integer Log wait latency (ms)
get_page integer Latency of get_page() calls (ms)

The read latency (page_reads column) measures the time from when the read request is sent to the file system thread until the read is complete and has been reported back to the execution thread. The write latency (page_writes) is calculated in a similar fashion. The size of the page read to or written from a Disk Data tablespace is always 32 KB.

Log wait latency (log_waits column) is the length of time a page write must wait for the undo log to be flushed, which must be done prior to each page write.

The pgman_time_track_stats table was added in NDB 8.0.19.