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Excerpts from this Manual The ndbinfo pgman_time_track_stats Table

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

The pgman_time_track_stats table contains the following columns:

  • node_id

    Unique node ID of this node in the cluster

  • block_number

    Block number (from blocks table)

  • block_instance

    Block instance number

  • upper_bound

    Upper bound

  • page_reads

    Page read latency (ms)

  • page_writes

    Page write latency (ms)

  • log_waits

    Log wait latency (ms)

  • get_page

    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.