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Oracle capacity planning with RRDTOOL

Ludovico — Mon, 25 May 2009 16:18:50 +0000

RRDize everything, chapter 2

Oracle Database Server has the most powerful system catalog that allows to query almost any aspect inside an oracle instance.
You can query many v$ fixed views at regular intervals and populate many RRD files through rrdtool: space usage, wait events. system statistics and so on…

Since release 10.1 Oracle has introduced Automatic Workload Repository, a finer version of old good Statspack.
No matter if you are using AWR or statspack, you can rely on their views to collect data for your RRDs.

If you are administering a new instance and you haven’t collected its statistics so far, you can query (as example) the DBA_HIST_BG_EVENT_SUMMARY view to gather all AWR data about wait events. Historical views could be useful also to collect historical data once a week rather than query the fixed views every few minutes doing the hard work twice (you and AWR).

The whole process of gathering performance data and update rrd files can be resumed into the following steps:

- connect to the database
- query the AWR’s views
- build and execute an rrdtool update command
- check if rrd file exists or create it
- update the rrd file

The less rrdtool update commands you will execute, the better the whole process will perform.
Do it in a language you are comfortable with and that supports easily connection descriptors.

Since I’m very comfortable with php, I did it this way.

This is a very basilar script that works greatly for me with good performances:

#!/usr/bin/php -f
< ?php                                         
 
define('WD','/opt/oracle/awr');
$cs         = $_SERVER['argv'][1];
$user       = 'mymonitoruser';
$pass       = 'mystrongpassword'; 
 
/* open a new connection */
$ds = oci_connect($user, $pass, $cs)
        or die ("Cannot connect to Oracle Database ".$cs."\n");
 
/* setting client nls environment */
$sql = "alter session set nls_timestamp_format='MM/DD/YY HH24:MI'";
$stmt = oci_parse($ds, $sql);
oci_execute($stmt);
oci_free_statement($stmt);                                         
 
/* create directory that will contain rrds (if not exists) */
if(!file_exists(WD.'/'.$cs))
                mkdir(WD.'/'.$cs);
if(!file_exists(WD.'/'.$cs.'/wait'))
                mkdir(WD.'/'.$cs.'/wait');                   
 
/* function to create new RRDs */
function createRRD($name, $interval, $cs) {
        $hb = $interval*5; //heartbeat
        $cmd="rrdtool create ".WD."/".$cs."/wait/${name}.rrd -s ".$interval." \
                -b \"now -3month\" DS:waits:DERIVE:$hb:0:U \
                DS:mswaited:DERIVE:$hb:0:U \
                RRA:AVERAGE:0.5:1:1440 RRA:AVERAGE:0.5:30:336 \
                RRA:AVERAGE:0.5:120:372 RRA:AVERAGE:0.5:720:730 \
                RRA:MIN:0.5:1:1440 RRA:MIN:0.5:30:336 \
                RRA:MIN:0.5:120:372 RRA:MIN:0.5:720:730 \
                RRA:MAX:0.5:1:1440 RRA:MAX:0.5:30:336 \
                RRA:MAX:0.5:120:372 RRA:MAX:0.5:720:730 \
                RRA:LAST:0.5:1:1440";
        //print $cmd."\n";
        return passthru($cmd);
}                                                                              
 
/* take the snapshot frequency from dba_hist_wr_control
 to create the RDD with correct heartbeat value */
$sql = 'select extract(hour from snap_interval)*3600 +
extract(minute from snap_interval)*60 as SEED from DBA_HIST_WR_CONTROL';
$stmt = oci_parse($ds, $sql);
oci_execute($stmt);
$row = oci_fetch_assoc($stmt);
$interval = $row['SEED'];
unset($row);
oci_free_statement($stmt);                                              
 
/* statement definition that will collect
 all snapshots for a certain wait event with more than
 a certain amonut of time waited.
 Gathering ALL EVENTS could be time consuming and useless.
 I fetch rows ordered by event_name rather
 then by date because I can update many values
 into the same rrd with very few rrdupdate commands
*/
$sql = 'select s.END_INTERVAL_TIME END_INTERVAL_TIME,
    g.EVENT_NAME, g.WAIT_CLASS, g.TOTAL_WAITS,
    round(g.TIME_WAITED_MICRO/1000) MS
  from DBA_HIST_SNAPSHOT s,
   dba_hist_bg_event_summary g,
   v$instance i
 where s.SNAP_ID=g.SNAP_ID and g.wait_class!=\'Idle\'
  and g.TIME_WAITED_MICRO>100000
  and s.instance_number=i.instance_number
  and s.instance_number=g.instance_number
 order by 2,1';                                      
 
/* default prefetch size (148) matches default snapshot retention (24hx7dd) */
$stmt = oci_parse($ds, $sql);
oci_set_prefetch($stmt, 148);
oci_execute($stmt);
 
$i=0;
$oldevent="";
while ($row = oci_fetch_assoc($stmt)) {
        if ($oldevent != $row['EVENT_NAME']) {
                //NEW EVENT DETECTED: WILL START A NEW UPDATE CMD
                if ($i != 0 &amp;&amp; !empty($cmd)) {
                        /* not the first occurrence,
                         I bet there's something in my buffer */
                        passthru($cmd);
                }
                $cleanName = preg_replace ("([^[:alnum:]_-])","_",$row['EVENT_NAME']);
                // if there is no rrd for this event, I create a new one
                if (!file_exists(WD."/".$cs."/wait/${cleanName}.rrd")) {
                        createRRD($cleanName, $interval, $cs);
                }
                /*
                * I initialize a new update command. This string act as a buffer: I append many
                * values to be updated so I'll update many values in a single command line:
                * less forks of rrdtool and less file opens: the whole update process has an
                * enormous improvement.
                */
                $precmd="rrdtool update ".WD."/".$cs."/wait/${cleanName}.rrd ";
                $lastcmd="rrdtool info ".WD."/".$cs."/wait/${cleanName}.rrd".
                        "| grep last_update | awk '{print \$NF}'";
                $last=trim(`$lastcmd`);
                printf ("%s - %s - last: %d\n", $row['EVENT_NAME'], $cleanName, $last);
                $i=0;
                $cmd=$precmd;
                $oldevent=$row['EVENT_NAME'];
        }
        $time=strtotime($row['END_INTERVAL_TIME']);
        //print "time: ".$time."  last: ".$last."\n";
        if ( $time &gt; $last ) {
                $cmd.=" ".$time.":".$row['TOTAL_WAITS'].":".$row['MS'];
                $i++;
        }
        if ($i &gt;= 40) {
                // when I reach 40 values per commandline I force
                // the update: next loop will reinitialize a new commandline.
                passthru($cmd);
                $cmd=$precmd;
                $i=0;
        }
        unset($row);
 
}
if ($i != 0) {
        /* one more update pending in my buffer */
        passthru($cmd);
}
oci_free_statement($stmt);
oci_close($ds);
?>

Depending on how many different wait events you have, you’ll have a certain number of rrd files:

# ls -l
total 3864
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 Streams_AQ__enqueue_blocked_on_low_memory.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 20 08:18 buffer_busy_waits.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 control_file_parallel_write.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 control_file_sequential_read.rrd
-rw-r--r-- 1 ludovico ludovico 165304 Apr 30 10:12 cursor__pin_S_wait_on_X.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 db_file_scattered_read.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 db_file_sequential_read.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 events_in_waitclass_Other.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 latch__cache_buffers_chains.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 latch__library_cache.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 11 13:22 latch__library_cache_lock.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 20 08:18 latch__redo_writing.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 latch__row_cache_objects.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 latch__shared_pool.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 library_cache_load_lock.rrd
-rw-r--r-- 1 ludovico ludovico 165304 Apr 15 13:17 library_cache_lock.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 log_buffer_space.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 log_file_parallel_write.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 log_file_sequential_read.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 log_file_single_write.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 log_file_switch_completion.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 11 13:22 log_file_sync.rrd
-rw-r--r-- 1 ludovico ludovico 165304 May 25 15:00 os_thread_startup.rrd

As you can see, they are not so big…

Once you have your data in rrd files, it’s quite simple to script even complex plots with several datasources. Everything depends on the results you want.
This script stack all my wait events for a certain instance: it takes the directory containing all the rrds as first argument and the number of hours we want to be plotted as second argument:

cs=$1
hours=${2:-148}
 
eventlist=`ls $cs/wait/*rrd`
 
colors[1]="#000000"
colors[2]="#000055"
colors[3]="#0000aa"
colors[4]="#0000ff"
colors[5]="#550055"
colors[6]="#aa00aa"
colors[7]="#ff00ff"
colors[8]="#550000"
colors[9]="#aa0000"
colors[10]="#ff0000"
colors[11]="#555500"
colors[12]="#aaaa00"
colors[13]="#ffff00"
colors[14]="#005500"
colors[15]="#00aa00"
colors[16]="#00ff00"
colors[17]="#005555"
colors[18]="#00aaaa"
colors[19]="#00ffff"
colors[20]="#555555"
colors[21]="#aaaaaa"
 
i=0
 
for event in $eventlist ; do
        if [ $i -eq 0 ] ; then
                end=`rrdtool info $event | grep last_update | awk '{print $NF}'`
                end=`rrdtool info $cs/wait/control_file_parallel_write.rrd | grep last_update | awk '{print $NF}'`
                cmd="rrdtool graph - -s end-${hours}hours -e $end  -v \"milliseconds waited\" -l 0 -w 640 -h 240 -t \"$cs WAIT PROFILE\""
                i=$(($i+1))
        fi
        color=${colors[$i]}
        echo $color
        evname=`basename $event | sed -e s/\.rrd\$//`
        cmd="$cmd  DEF:$evname=$event:mswaited:AVERAGE"
        cmd="$cmd  AREA:${evname}${color}:"$evname":STACK"
        i=$(($i+1))
        if [ $i -eq 20 ] ; then
                i=1
        fi
done
        cmd="$cmd  |display /dev/input"
        echo $cmd
        eval $cmd
exit

The resulting command is very long:

rrdtool graph - -s end-148hours -e 1243252800 \
 -v "milliseconds waited" -l 0 -w 640 -h 240 -t "mydb WAIT PROFILE"\
 DEF:Streams_AQ__enqueue_blocked_on_low_memory=mydb/wait/Streams_AQ__enqueue_blocked_on_low_memory.rrd:mswaited:AVERAGE \
 AREA:Streams_AQ__enqueue_blocked_on_low_memory#000000:Streams_AQ__enqueue_blocked_on_low_memory:STACK\
 DEF:buffer_busy_waits=mydb/wait/buffer_busy_waits.rrd:mswaited:AVERAGE \
 AREA:buffer_busy_waits#000055:buffer_busy_waits:STACK\
 DEF:control_file_parallel_write=mydb/wait/control_file_parallel_write.rrd:mswaited:AVERAGE \
 AREA:control_file_parallel_write#0000aa:control_file_parallel_write:STACK\
 DEF:control_file_sequential_read=mydb/wait/control_file_sequential_read.rrd:mswaited:AVERAGE \
 AREA:control_file_sequential_read#0000ff:control_file_sequential_read:STACK\
 DEF:cursor__pin_S_wait_on_X=mydb/wait/cursor__pin_S_wait_on_X.rrd:mswaited:AVERAGE \
 AREA:cursor__pin_S_wait_on_X#550055:cursor__pin_S_wait_on_X:STACK\
 DEF:db_file_scattered_read=mydb/wait/db_file_scattered_read.rrd:mswaited:AVERAGE \
 AREA:db_file_scattered_read#aa00aa:db_file_scattered_read:STACK\
 DEF:db_file_sequential_read=mydb/wait/db_file_sequential_read.rrd:mswaited:AVERAGE \
 AREA:db_file_sequential_read#ff00ff:db_file_sequential_read:STACK\
 DEF:events_in_waitclass_Other=mydb/wait/events_in_waitclass_Other.rrd:mswaited:AVERAGE \
 AREA:events_in_waitclass_Other#550000:events_in_waitclass_Other:STACK\
 DEF:latch__cache_buffers_chains=mydb/wait/latch__cache_buffers_chains.rrd:mswaited:AVERAGE \
 AREA:latch__cache_buffers_chains#aa0000:latch__cache_buffers_chains:STACK\
 DEF:latch__library_cache=mydb/wait/latch__library_cache.rrd:mswaited:AVERAGE \
 AREA:latch__library_cache#ff0000:latch__library_cache:STACK\
 DEF:latch__library_cache_lock=mydb/wait/latch__library_cache_lock.rrd:mswaited:AVERAGE \
 AREA:latch__library_cache_lock#555500:latch__library_cache_lock:STACK\
 DEF:latch__redo_writing=mydb/wait/latch__redo_writing.rrd:mswaited:AVERAGE \
 AREA:latch__redo_writing#aaaa00:latch__redo_writing:STACK\
 DEF:latch__row_cache_objects=mydb/wait/latch__row_cache_objects.rrd:mswaited:AVERAGE \
 AREA:latch__row_cache_objects#ffff00:latch__row_cache_objects:STACK\
 DEF:latch__shared_pool=mydb/wait/latch__shared_pool.rrd:mswaited:AVERAGE \
 AREA:latch__shared_pool#005500:latch__shared_pool:STACK\
 DEF:library_cache_load_lock=mydb/wait/library_cache_load_lock.rrd:mswaited:AVERAGE \
 AREA:library_cache_load_lock#00aa00:library_cache_load_lock:STACK\
 DEF:library_cache_lock=mydb/wait/library_cache_lock.rrd:mswaited:AVERAGE \
 AREA:library_cache_lock#00ff00:library_cache_lock:STACK\
 DEF:log_buffer_space=mydb/wait/log_buffer_space.rrd:mswaited:AVERAGE \
 AREA:log_buffer_space#005555:log_buffer_space:STACK\
 DEF:log_file_parallel_write=mydb/wait/log_file_parallel_write.rrd:mswaited:AVERAGE \
 AREA:log_file_parallel_write#00aaaa:log_file_parallel_write:STACK\
 DEF:log_file_sequential_read=mydb/wait/log_file_sequential_read.rrd:mswaited:AVERAGE \
 AREA:log_file_sequential_read#00ffff:log_file_sequential_read:STACK\
 DEF:log_file_single_write=mydb/wait/log_file_single_write.rrd:mswaited:AVERAGE \
 AREA:log_file_single_write#000000:log_file_single_write:STACK\
 DEF:log_file_switch_completion=mydb/wait/log_file_switch_completion.rrd:mswaited:AVERAGE \
 AREA:log_file_switch_completion#000055:log_file_switch_completion:STACK\
 DEF:log_file_sync=mydb/wait/log_file_sync.rrd:mswaited:AVERAGE \
 AREA:log_file_sync#0000aa:log_file_sync:STACK\
 DEF:os_thread_startup=mydb/wait/os_thread_startup.rrd:mswaited:AVERAGE \
 AREA:os_thread_startup#0000ff:os_thread_startup:STACK |display /dev/input

This is the resulting graph:

OHHHHHHHHHHHH COOOOL!!!

Any comment is appreciated! thanks

Quick Oracle Dataguard check script

Ludovico — Mon, 05 Jan 2009 15:49:10 +0000

Oracle Dataguard has his own command-line dgmgrl to check the whole dataguard configuration status.
At least you should check that the show configuration command returns SUCCESS.

This is an hypothetic script:

#!/bin/bash
export ORACLE_HOME=/u1/app/oracle/product/10.2.0
export ORACLE_SID=orcldg
result=`echo "show configuration;" | \
  $ORACLE_HOME/bin/dgmgrl sys/strongpasswd | \
  grep -A 1 "Current status for" | grep -v "Current status for"`
if [ "$result" = "SUCCESS" ] ; then
    exit 0
else
    exit 1
fi

Another script should check for the gap between production online log and the log stream received by the standby database. This can be accomplished with v$managed_standby view.
The Total Block Gap between production and standby can be calculated this way:
Sum all blocks from v$archived_logs where seq# between Current Standby Seq# and Current Production Seq#. Then add current block# of the production LGWR process and subtract current block# from RFS standby process. This gives you total blocks even if there is a log sequence gap between sites.
This is NOT the gap of online log APPLIED to the standby database. THIS IS THE GAP OF ONLINE LOG TRANSMITTED TO THE STANDBY RFS PROCESS and can be used to monitor your dataguard transmission from production to disaster recovery environment.

This is an excerpt of such script (please take care that it does not check against RFS failures, so it can fails when RFS is not alive):

#!/u1/app/oracle/product/10.2.0/perl/bin/perl -w
use DBI;
use DBD::Oracle qw(:ora_session_modes);
# DB connection #
my $prod  = "orclprod";
my $stby = "orcldr";
my $prodh;
unless ($prodh = DBI->connect('dbi:Oracle:'.$prod,
  'sys', 'strongpassword',
  {PrintError=>0, AutoCommit => 0,
  ora_session_mode => ORA_SYSDBA}))  {
    print "Error connecting to DB: $DBI::errstr\n";
        exit(1);
}
$prodh->{RaiseError}=1;
 
my $stbyh;
unless ($stbyh = DBI->connect('dbi:Oracle:'.$stby,
  'sys', 'strongpassword',
  {PrintError=>0, AutoCommit => 0,
  ora_session_mode => ORA_SYSDBA}))  {
    print "Error connecting to DB: $DBI::errstr\n";
        $prodh->disconnect;
        exit(1);
}
$stbyh->{RaiseError}=1;
 
my $sth;
### query prod
$sth = $prodh->prepare( < <EOSQL );
        select SEQUENCE#, BLOCK# from v\$managed_standby
        where process='LGWR'
EOSQL
$sth->execute();
my ($psequence, $pblock) = $sth->fetchrow_array();
$sth->finish();
### query stdby
$sth = $stbyh->prepare( < <EOSQL );
        select SEQUENCE#, BLOCK# from v\$managed_standby
        where process='RFS' and client_process='LGWR'
EOSQL
$sth->execute();
my ($ssequence, $sblock) = $sth->fetchrow_array();
$sth->finish();
 
printf ("PROD   : %10d %10d\n", $psequence, $pblock);
printf ("STANDBY: %10d %10d\n", $ssequence, $sblock);
 
$sth = $stbyh->prepare( < <EOSQL );
        select nvl(sum(blocks),0)
        + $pblock - $sblock as BLOCK_GAP
    from v\$archived_log
        where sequence# between $ssequence and $psequence
EOSQL
$sth->execute();
my ($blockgap) = $sth->fetchrow_array();
$sth->finish();
printf ("%-10d blocks gap\n", $blockgap);
 
$stbyh->disconnect;
$prodh->disconnect;

Any comment is appreciated!

Oracle RAC Standard Edition to achieve low cost and high performance

Ludovico — Thu, 27 Nov 2008 23:43:04 +0000

I finished today to create a new production environment based on 2 Linux serverX86_64 and running Oracle RAC 10gR2. (I know, there is 11g right now, but I’m a conservative!)
Wheeew, I just spent a couple of hours applying all the recommended patches!
We choosed 2 nodes with a maximum of 2 multi-core processors each one so we can license Standard Edition instead of Enterprise Edition. 64bits addressing allow us to allocate many gigabytes of SGA. I’m starting with 5Gb but I think we’ll need more. And a set of 6×300Gb 15krpms disks (it can be expanded with more disks and more shelves).
This configuration keeps low the total cost of ownership but achieves best performance.
Due to disks layout, costs and needed usable storage, we had to configure one huge RAID5 on the SAN with multi-path. I decided anyway to create 2 ASM disk groups (ASM is mandatory for Standard Edition RAC), one for the DB, the second one for the recovery area. With spare disks we should have enough availability and even if it’s a RAID5 I saw good write performances (>150M/s).

Welcome new RAC, I hope we’ll feel good together!