onstat -F command: Print counts

Use the onstat -F command to display a count for each type of write that flushes pages to disk.


Syntax:

>>-onstat-- -F-------------------------------------------------><

Example output

Figure 1. onstat -F command output

Fg Writes     LRU Writes    Chunk Writes 
0             330           7631         

address  flusher  state  data  # LRU  Chunk  Wakeups  Idle Time
c7c8850  0        I      0     9      29     16116    16093.557
      states: Exit Idle Chunk Lru

Output description

You can interpret output from this option as follows:

Fg Writes

Is the number of times that a foreground write occurred

LRU Writes

Is the number of times that an LRU write occurred

Chunk Writes

Is the number of times that a chunk write occurred

address

Is the address of the user structure assigned to this page-cleaner thread

flusher

Is the page-cleaner number

state

Uses the following codes to indicate the current page-cleaner activity:

C: Chunk write
E: Exit
I: Cleaner is idle
L: LRU queue

The exit code indicates either that the database server is performing a shutdown or that a page cleaner did not return from its write in a specific amount of time. When an operation fails to complete within the allotted time, this situation is known as a time-out condition. The database server does not know what happened to the cleaner, so it is marked as exit. In either case, the cleaner thread eventually exits.

data

Provides additional information in concert with the state field

If state is C, data is the chunk number to which the page cleaner is writing buffers. If state is L, data is the LRU queue from which the page cleaner is writing. The data value is displayed as a decimal, followed by an equal sign, and repeated as a hexadecimal.

#LRU

Corresponds to the onstat -g ath thread ID output

Chunk

Number of chunks cleaned

Wakeups

Number of times the flusher thread was awoken

Idle Time

Time in seconds the flusher thread has been idle