DBA Scripts - Very Useful - 2. Disk I/O, Events, Waits

Here are some scripts related to Disk I/O, Events, Waits .

Datafile I/O

DATAFILE I/O NOTES:

  File Name - Datafile name

  Physical Reads - Number of physical reads

  Reads % - Percentage of physical reads

  Physical Writes - Number of physical writes

  Writes % - Percentage of physical writes

  Total Block I/O's - Number of I/O blocks

  Use this report to identify any "hot spots" or I/O contention

select       NAME,

               PHYRDS "Physical Reads",

               round((PHYRDS / PD.PHYS_READS)*100,2) "Read %",

               PHYWRTS "Physical Writes",

               round(PHYWRTS * 100 / PD.PHYS_WRTS,2) "Write %",

               fs.PHYBLKRD+FS.PHYBLKWRT "Total Block I/O's"

from (

               select       sum(PHYRDS) PHYS_READS,

                               sum(PHYWRTS) PHYS_WRTS

               from        v$filestat

               ) pd,

               v$datafile df,

               v$filestat fs

where       df.FILE# = fs.FILE#

order        by fs.PHYBLKRD+fs.PHYBLKWRT desc

SGA Stats

SGA STAT NOTES:

  Statistic Name - Name of the statistic

  Bytes - Size

select       NAME,

               BYTES

from        v$sgastat

order        by NAME

Sort Stats

SORT NOTES:

  Sort Parameter - Name of the sort parameter

  Value - Number of sorts

  sorts (memory) - The number of sorts small enough to be performed entirely in sort areas without using temporary segments.

  sorts (disk) - The number of sorts that were large enough to require the use of temporary segments for sorting.

  sorts (rows) - Number of sorted rows

  The memory area available for sorting is set via the SORT_AREA_SIZE and SORT_AREA_RETAINED_SIZE init.ora parameters.

select       NAME,

               VALUE

from        v$sysstat

where       NAME like 'sort%'

All Events

SYSTEM EVENT (ALL) NOTES:

  Event Name - Name of the event

  Total Waits - Total number of waits for the event

  Total Timeouts - Total number of timeouts for the event

  Time Waited - The total amount of time waited for this event, in hundredths of a second

  Average Wait - The average amount of time waited for this event, in hundredths of a second

select       EVENT,

               TOTAL_WAITS,

               TOTAL_TIMEOUTS,

               TIME_WAITED,

               round(AVERAGE_WAIT,2) "Average Wait"

from        v$system_event

order        by TOTAL_WAITS

All Statistics

SYSTEM STATISTICS (ALL) NOTES:

  Stat# - Number of the statistic

  Name - Name of the statistic

  Class - Statistic class: 1 (User), 2 (Redo), 4 (Enqueue), 8 (Cache), 16 (OS), 32 (Parallel Server), 64 (SQL), 128 (Debug)

  Value - Value of the statistic

select       STATISTIC#,

               NAME,

               CLASS,

               VALUE

from        v$sysstat

Wait Stats

WAIT STATISTIC NOTES:

  Class - Class of block subject to contention

  Count - Number of waits by this OPERATION for this CLASS of block

  Time -Sum of all wait times for all the waits by this OPERATION for this CLASS of block

  Data Blocks - Usually occurs when there are too many modified blocks in the buffer cache; reduce contention by adding DBWR processes.

  Free List - May occur if multiple data loading programs run simultaneously.

  Segment Header - May occur when may full table scans execute simultaneously with data loading processes; aggravated by the parallel options. Reschedule data loading jobs to reduce contention;

  Sort Block - Rarely seen except when the Parallel Query option is used; reduce contention by reducing the degree of parallelism or decreasing the SORT_AREA_SIZE init.ora parameter setting.

  Undo Block - Very rarely occurs; may be caused by multiple users updating records in the same data block at a very fast rate; contention can usually be resolved by increasing the PCTFREE of the tables being modified.

  Undo Header - May occur if there are not enough rollback segments to support the number of concurrent transactions.

select       CLASS,

               COUNT,

               TIME

from        v$waitstat

order        by CLASS