DBA SGA+PGA Memory Configuration

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Description
Categories: Enginatics
Repository: Github
Current SGA and PGA memory configuration in gigabytes.

A frequent configuration problem is not making full use of the available hardware resources, especially the physical RAM of the database server.
This report shows the servers SGA, PGA and CPU configuration in comparison to the available hardware.
For maximum performance, configure the SGA+PGA to use the full available memory of your server minus a few gig for OS level caching, e.g. for writing and reading of PLSQL output files on the DB node and for process memory (an estimated 4MB per process, see below).

Oracle's performance tuning guide:
https://docs.oracle.com/en/database/oracle/oracle-database/12.2/tgdba/database-memory-allocation.html ...  Current SGA and PGA memory configuration in gigabytes.

A frequent configuration problem is not making full use of the available hardware resources, especially the physical RAM of the database server.
This report shows the servers SGA, PGA and CPU configuration in comparison to the available hardware.
For maximum performance, configure the SGA+PGA to use the full available memory of your server minus a few gig for OS level caching, e.g. for writing and reading of PLSQL output files on the DB node and for process memory (an estimated 4MB per process, see below).

Oracle's performance tuning guide:
https://docs.oracle.com/en/database/oracle/oracle-database/12.2/tgdba/database-memory-allocation.html

Oracle's exadata best practices whitepaper:
SUM of databases (SGA_TARGET + PGA_AGGREGATE_TARGET) + 4 MB * (Maximum PROCESSES) < Physical Memory per Database Node

Tom Kyte's recommendation:
"... if you want it all automatic, give ALL FREE MEMORY on your machine to the SGA and be done with it. No more monitoring, no more thinking about how it could be, should be, would be used.
Set the PGA aggregate target and the SGA target to be a tad less than physical memory on the machine and you are done."
https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:30011178429375

The report also shows the status of system statistics.
select * from sys.aux_stats$

If CPUSPEEDNW still shows the default of 4096, it either means that the stats have never been gathered or it could also mean that your storage is too fast to gather them with the standard NOWORKLOAD method and you should set reasonable values manually then.
exec dbms_stats.gather_system_stats();
exec dbms_stats.set_system_stats('IOSEEKTIM',1);
exec dbms_stats.set_system_stats('IOTFRSPEED',85782);

There is also an Exadata mode, considering the faster storage correctly and updating the MBRC too
exec dbms_stats.gather_system_stats(‘EXADATA');

The following command checks if hugepages are configured and how many are in use:
grep Huge /proc/meminfo
https://access.redhat.com/solutions/320303

To configure hugepages, set the vm.nr_hugepages in the /etc/sysctl.conf file and hard and soft memlock in /etc/security/limits.conf for the oracle user.
/etc/sysctl.conf
vm.nr_hugepages = SGA GB x 512 + 5
/etc/security/limits.conf
oracle soft memlock (SGA GB x 512 + 5) * 2048
oracle hard memlock (SGA GB x 512 + 5) * 2048
https://www.carajandb.com/en/2016/09/22/7-easy-steps-to-configure-hugepages-for-your-oracle-database-server/

Check if all database parameters are set according to Oracle's requirement:
Database Initialization Parameters for Oracle E-Business Suite Release 12 (Note 396009.1)
https://support.oracle.com/rs?type=doc&id=396009.1

To perform this check automatically, install and run Oracle's 'Database Performance and Statistics Analyzer' concurrent program (Doc ID 2126712.1)
https://support.oracle.com/rs?type=doc&id=2126712.1   more 
with dhss as (
select distinct
dhss.instance_number inst_id,
sum(dhss.iowait_delta) over (partition by dhss.instance_number)/1000000 iowait,
sum(dhss.cpu_time_delta) over (partition by dhss.instance_number)/1000000 cpu_time,
(max(cast(dhs.end_interval_time as date)) over (partition by dhss.instance_number)-min(cast(dhs.begin_interval_time as date)) over (partition by dhss.instance_number))*86400 time_interval
from
dba_hist_snapshot dhs,
dba_hist_sqlstat dhss,
dba_hist_sqltext dhst
where
1=1 and
dhs.begin_interval_time>=sysdate-7 and
dhst.command_type not in (47) and
dhs.dbid=dhss.dbid and
dhs.instance_number=dhss.instance_number and
dhs.snap_id=dhss.snap_id and
dhss.dbid=dhst.dbid and
dhss.sql_id=dhst.sql_id
)
select
*
from
(
select
x.inst_id,
x.name,
case when x.name not like '%cpu%' then x.value/1024/1024/1024 else x.value end value
from
(
select go.inst_id, 'cpu physical' name, go.value, 11 order_by from gv$osstat go where go.stat_name='NUM_CPUS' union all
select go.inst_id, 'memory physical' name, go.value, 1 order_by from gv$osstat go where go.stat_name='PHYSICAL_MEMORY_BYTES' union all
select go.inst_id, 'memory unused' name, go.value-(select sum(gp.value) from gv$parameter gp where go.inst_id=gp.inst_id and gp.name in ('sga_target','memory_target','pga_aggregate_target')) value, 2 order_by from gv$osstat go where go.stat_name='PHYSICAL_MEMORY_BYTES' union all
select gp.inst_id, gp.name, to_number(gp.value) value,
decode(gp.name,
'cpu_count',12,
'sga_max_size',3,
'sga_target',4,
'pga_aggregate_target',5,
'pga_aggregate_limit',6,
'memory_max_target',7,
'memory_target',8,
'result_cache_max_size',9
) order_by
from gv$parameter gp where gp.name in ('cpu_count','pga_aggregate_limit','pga_aggregate_target','sga_max_size','sga_target','memory_max_target','memory_target','result_cache_max_size')
) x
order by
x.inst_id,
x.order_by
)
union all
select * from (select gsi.inst_id, 'free SGA', gsi.bytes/1024/1024/1024 value from gv$sgainfo gsi where gsi.name='Free SGA Memory Available' order by gsi.inst_id)
union all
select * from (
select
gi.inst_id,
'PGA record date: '||least(gi.startup_time,(select min(dhs.begin_interval_time) from dba_hist_snapshot dhs where vd.dbid=dhs.dbid and gi.instance_number=dhs.instance_number)) name,
null value
from
gv$instance gi,
v$database vd
order by gi.inst_id
)
union all
select * from (select
gi.inst_id,
'average PGA' name,
(select avg(dhp.value)/1024/1024/1024 from dba_hist_pgastat dhp where vd.dbid=dhp.dbid and gi.instance_number=dhp.instance_number and dhp.name='total PGA allocated') value
from
gv$instance gi,
v$database vd
order by gi.inst_id
)
union all
select * from (
select
gi.inst_id,
'maximum PGA' name,
(select max(dhp.value)/1024/1024/1024 from dba_hist_pgastat dhp where vd.dbid=dhp.dbid and gi.instance_number=dhp.instance_number and dhp.name='maximum PGA allocated') value
from
gv$instance gi,
v$database vd
order by gi.inst_id
)
union all
select * from (select dhss.inst_id, 'Wait IO percentage' name, dhss.iowait/(dhss.iowait+dhss.cpu_time)*100 value from dhss order by dhss.inst_id)
union all
select * from (select dhss.inst_id, 'Wait IO average active sessions' name, dhss.iowait/time_interval value from dhss order by dhss.inst_id)
union all
select * from (select dhss.inst_id, 'CPU average active sessions' name, dhss.cpu_time/time_interval value from dhss order by dhss.inst_id)
union all
select
to_number(null) inst_id,
case when ass.pname='DSTART' then 'System Stats record date: '||ass.pval2 else ass.pname end name,
to_number(decode(ass.pname,'DSTART',null,ass.pval1)) value
from sys.aux_stats$ ass
where
ass.pname in ('DSTART','CPUSPEEDNW','IOSEEKTIM','IOTFRSPEED','MBRC')
union all
select to_number(null) inst_id, 'Use large pages: '||vp.value name, null value from v$parameter vp where vp.name='use_large_pages' union all
select to_number(null) inst_id, 'Pack License: '||vp.value name, null value from v$parameter vp where vp.name='control_management_pack_access' union all
select distinct to_number(null) inst_id, 'AWR Report last usage date: '||max(dfus.last_usage_date) over () name, null value from dba_feature_usage_statistics dfus where dfus.name='AWR Report' and dfus.dbid in (select vd.dbid from v$database vd) union all
select distinct to_number(null) inst_id, 'AWR Report usages' name, sum(dfus.detected_usages) over () value from dba_feature_usage_statistics dfus where dfus.name='AWR Report' and dfus.dbid in (select vd.dbid from v$database vd) union all
select to_number(null) inst_id, 'Database size' name, sum((select vp.value from v$parameter vp where vp.name like 'db_block_size')*dtum.used_space)/1024/1024/1024 value from dba_tablespace_usage_metrics dtum
Parameter NameSQL textValidation
Container Data
dhs.dbid=(select vd.dbid from v$database vd)
LOV
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