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DB12c: All You Need to Know About the Resource Manager

The document provides an overview of Oracle 12c's Resource Manager, highlighting its features, benefits, and operational scenarios. It discusses how the Resource Manager allows prioritization of database sessions to optimize CPU resource allocation and manage workload efficiently. Additionally, it outlines the complexities and solutions involved in resource management, particularly in multi-tenant environments.

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Overview of the Resource Manager and its features. Introduced by Māris Elsiņš, outlining the agenda.

Discussed problems in DB session prioritization and CPU resource management, including CPU starvation scenarios and their impacts.

Detailed concepts of Resource Manager including consumer groups and directives for resource allocation.

Introduction of new 12c features like automated consumer group switching, enhancing resource management.

Explanation of CDB and PDB resource plans, the distribution of resources, and conversion from non-CDB.

Discussion about Resource Manager overhead, testing scripts, and methodologies for evaluating performance.

Experimental results on different resource plans highlighting CPU allocation accuracy and performance impacts.

Summarized findings indicating RM overhead is negligible, along with performance insights and recommendations.

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DB12C: ALL YOU NEED TO KNOW ABOUT THE RESOURCE MANAGER Māris Elsiņš Lead Database Consultant Pythian @MarisElsins
MARIS ELSINS Lead Database Consultant at Pythian Oracle [Apps] DBA since 2005 Speaker at conferences since 2007 @MarisElsins elsins@pythian.com http://bit.ly/getMOSPatch
ABOUT PYTHIAN 3 Founded  in  1997,  Pythian  is  a  global   leader  in  data  consulting  and  managed   services  specializing    in  planning,   optimizing,  and  managing  mission-­ critical  data  systems Top  5%  talent  worldwide     10  Oracle  ACEs 3  Oracle  ACE  Directors 18  years  in  business   450+  employees 250+  customers  worldwide  
AGENDA • Features of the Resource Manager • The new 12c-stuff • Consolidations using Oracle Multitenant • Overhead of the RM 4
FEATURES OF THE RESOURCE MANAGER 5
THE PROBLEM • OS  doesn’t  care  enough  about  DB  sessions/processes   according  to  what  business  requires – Assigns  the  same  priority  to  all  processes – CPU  resources  are  equally  distributed  among  all  processes – Inability  to  manage  DB-­specific  resources/situations • CPU  distribution  among  sessions,  Parallel  Execution   Servers,  Active  session  Pool  and  Queuing,  Undo  usage,   Runaway  Queries,  Blocking  sessions – Context  switching  overhead  when  many  processes  running • Problems  start  when  there’s  not  enough  CPU  for   everyone • CPU  starvation  can  be  hard  to  recover  from (the  snowball  effect) • CPU  starvation  makes  online  troubleshooting  hard  to  do 6
PROBLEM SCENARIOS - QUIZ TIME! • Running  reports  causes  too  much  load  on  the  OLTP  system. • One  of  the  sessions  allocate  all  parallel  query  slaves  therefore  other   sessions  don’t  get  any • Application  support  team  runs  heavy  queries  to  analyze  the  data   leaving  less  resources  for  online  transactions • Wide  search  criteria  cause  “hangs”  in  the  search  form • 3  of  8  CPU  cores  are  idle,  my  query  runs  without  parallel  execution,   I  could  use  the  idle  CPUs  to  provide  results  faster • Users  don’t  log  out  and  leave  idle  sessions • My  batch  process  requires  DOP=8  to  complete  in  time,  but  it’s   downgraded  to  smaller  DOP  if  enough  parallel  slaves  are  not  available • My  query  is  very  important.  It’s  IO  requests  have  to  be  prioritized! • Sessions  with  incomplete  transactions  have  locked  some  rows  and   other  sessions  have  stuck. 7
THE BASIC CONCEPTS • Resource Manager – Included in Oracle EE license – Allows prioritization of sessions according to the defined business requirements – Allows defining the guaranteed amount of allocated resources for each type of sessions (consumer group) – Resources not used by higher priority sessions, can be used by lower priority sessions • Prioritizationis achieved by changing the process states to running/sleeping – DBRM / VKRM (CPU scheduling) – Semaphores (wake up sleeping processes) – CPU quantum (_dbrm_quantum) • Resource manager does not solve the «lack of CPU resources» problem, it just controls the execution queue • Resource manager uses some resources too, the last part of the presentation will estimate the overhead 8
THE BASIC CONCEPTS 9 • Consumer group – Set of sessions having similar requirements for server resources – Resources are allocated to the consumer group, not individual sessions – DBA_RSRC_CONSUME_GROUPS • Directives – Rules that define resource allocation to the consumer group – DBA_RSRC_PLAN_DIRECTIVES • Resource plan – Set of directives defining the distribution of resources among consumer groups – DBA_RSRC_PLANS
SQL> select event, count(*) from v$session group by event order by 2 desc; EVENT COUNT(*) ---------------------------------------------------------------- ---------- resmgr:cpu quantum 25 rdbms ipc message 23 Space Manager: slave idle wait 16 SQL*Net message from client 9 EMON slave idle wait 5 DIAG idle wait 2 LGWR worker group idle 2 GCR sleep 2 Streams AQ: waiting for time management or cleanup tasks 1 VKTM Logical Idle Wait 1 AQPC idle 1 Streams AQ: qmn coordinator idle wait 1 VKRM Idle 1 PING 1 ... 23 rows selected. RESMGR:CPU QUANTUM WHY IS MY SESSION NOT RUNNING? 10
RESMGR:CPU QUANTUM WHY IS MY SESSION NOT RUNNING? SQL> select event, status, count(*) from v$session where event='resmgr:cpu quantum' group by event, status order by 1,2; EVENT STATUS COUNT(*) ------------------ -------- ---------- resmgr:cpu quantum ACTIVE 25 11
RESMGR:CPU QUANTUM WHY IS MY SESSION NOT RUNNING? 12 SQL> select event, status, state, count(*) from v$session where event='resmgr:cpu quantum' group by event, status, state order by 1,2,3; EVENT STATUS STATE COUNT(*) ------------------ -------- ------------------- ---------- resmgr:cpu quantum ACTIVE WAITED KNOWN TIME 7 resmgr:cpu quantum ACTIVE WAITED SHORT TIME 16 resmgr:cpu quantum ACTIVE WAITING 2
RESMGR:CPU QUANTUM WHY IS MY SESSION NOT RUNNING? • EVENT values are often misinterpreted in: – V$SESSION – V$SESSION_WAIT • Common mistake is to forget about v$session.STATE! • If STATE = 'WAITING’, only then the session is waiting – EVENT shows what the session is waiting for – STATUS can be ACTIVE or INACTIVE • If STATE = 'WAITED % TIME’ .. – and STATUS = 'ACTIVE', the session is ON CPU – and STATUS != 'ACTIVE', the session is not running THIS IS TRUE FOR ALL WAITEVENTS 13
FEATURES 9.2 10.2 11.1 11.2 12.1 CPU resource allocation J J J J J Limit of the degree of parallelism J J J J J active session pool J J J J J Automated change of consumer group if session has used or is estimated to use the defined amount of resources CPU,   Est  CPU CPU,   Est  CPU CPU, Est CPU,   IO_MB,   IO_REQ CPU, Est CPU,   IO_MB,   IO_REQ CPU, Est  CPU,   IO_MB,   IO_REQ, LIO, Ela, Est  Ela Limit of estimated execution time J J J J J Limit size of undo used by uncommitted sessions J J J J J Termination of idle sessions J J J J Termination of idle blocking sessions J J J J L0 70% CPU _ORACLE_BACKGROUND_GROUP_ hidden consumer group for background processes J J J at  90% Instance caging /CPU_COUNT + resource plan/ J J Max CPU Utilization limit J J Parallel Statement Queue J J LOG_ONLY “switch group” for real-time SQL monitoring J Simplified automated consumer group switching J 14
THE NEW 12C-STUFF 15
AUTOMATED CONSUMER GROUP SWITCHING 12C: MORE OPTIONS • Logical IO • Elapsed time • Estimated elapsed time • Real-time SQL monitoring – LOG_ONLY 16
17 SELECT executions, end_of_fetch_count, elapsed_time/px_servers elapsed_time, cpu_time /px_servers cpu_time, buffer_gets /executions buffer_gets FROM (SELECT SUM(executions) AS executions, sum ( CASE WHEN px_servers_executions > 0 THEN px_servers_executions ELSE executions END) AS px_servers, SUM(end_of_fetch_count) AS end_of_fetch_count, SUM(elapsed_time) AS elapsed_time, SUM(cpu_time) AS cpu_time, SUM(buffer_gets) AS buffer_gets FROM gv$sql WHERE executions > 0 AND sql_id = :1 AND parsing_schema_name = :2 ) AUTOMATED CONSUMER GROUP SWITCHING ESTIMATED ELAPSED TIME
AUTOMATED CONSUMER GROUP SWITCHING ESTIMATED ELAPSED TIME 18 SELECT executions, end_of_fetch_count, elapsed_time/px_servers elapsed_time, cpu_time /px_servers cpu_time, buffer_gets /executions buffer_gets FROM (SELECT SUM(executions_delta) AS EXECUTIONS, SUM( CASE WHEN px_servers_execs_delta > 0 THEN px_servers_execs_delta ELSE executions_delta END) AS px_servers, SUM(end_of_fetch_count_delta) AS end_of_fetch_count, SUM(elapsed_time_delta) AS ELAPSED_TIME, SUM(cpu_time_delta) AS CPU_TIME, SUM(buffer_gets_delta) AS BUFFER_GETS FROM DBA_HIST_SQLSTAT s, V$DATABASE d, DBA_HIST_SNAPSHOT sn WHERE s.dbid = d.dbid AND bitand(NVL(s.flag, 0), 1) = 0 AND sn.end_interval_time > (SELECT SYS imestamp at TIME ZONE dbtimezone FROM dual) - 7 AND s.sql_id = :1 AND s.snap_id = sn.snap_id AND s.instance_number = sn.instance_number AND s.dbid = sn.dbid AND parsing_schema_name = :2)
REAL-TIME SQL MONITORING IMPROVEMENTS LOG_ONLY – RESERVED CONSUMER GROUP NAME • Analyze the RM activity (V$SQL_MONITOR) – RM_LAST_ACTION – RM_LAST_ACTION_REASON – RM_LAST_ACTION_TIME – RM_CONSUMER_GROUP • Understand how and why the consumer groups are switched • V$SQL_MONITOR.QUEUING_TIME • The RM_% values are not presented in SQL Monitor reports or in EM 12c CC 19
CONSUMER GROUP SWITCHING SIMPLIFIED PRIVILEGES • In pre-12c any kind of switching required explicit privilege – DBMS_RESOURCE_MANAGER_PRIVS. GRANT_SWITCH_CONSUMER_GROUP • 12.1 privileges included for: – Consumer group mappings – Condition based on SWITCH_GROUP • What it means to DBAs? – Removes redundant work – Simplicity – More flexibility as explicit grants can be avoided 20
CDB and PDB Resource Plans CONSOLIDATION USING ORACLE MULTITENANT 21
CDB RESOURCE PLAN • CDB resource plan – Defines how resources are distributed between PDBs – Shares – Minimum portion of resources allocated to the PDB – Additional Limits • Utilization_limit • Parallel_server_limit (%) • CDB Plan Directives (in DEFAULT_CDB_PLAN) – ORA$DEFAULT_PDB_DIRECTIVE – default • Shares=1, utilization_limit=100, parallel_server_limit=100 – ORA$AUTOTASK – for autotasks in root container • Shares=1, utilization_limit=90, parallel_server_limit=100 • User-defined directives for exceptional PDBs
PDB RESOURCE PLAN • Allows to use the resources proportionally to the allocated shares • Works just like a resource plan for non-CDB • Few restrictions – A PDB resource plan can't have sub-plans. – A PDB resource plan can have a maximum of eight consumer groups. – A PDB resource plan cannot have a multi-level scheduling policy. • So we need to take action to re-implement the resource plans when we switch from non-CDB to the CDB? – Not always! It happens automatically, but how? 23
CONVERTING NON-CDB PLANS TO PDB PLANS MULTI-LEVEL SCHEDULING POLICIES ARE NOT ALLOWER • Automatically when the non-CDB is converted into PDB – $ORACLE_HOME/rdbms/admin/noncdb_to_pdb.sql – The original plan and plan directivesare saved with STATUS=LEGACY – A new plan is added with the same name and STATUS={null} • Algorithm is not documented, but appears to be simple enough: – Adjust allocated CPU% on each level • Reduce each level to 75% proportionally • Leave it as is if it’s already lower than 75% – The “free portion” is passed to the lower level and split per calculated percentages, the remaining portion is passed down – The last level get’s all remaining resources 24
CONVERTING NON-CDB TO PDB EXAMPLE 1 25
CONVERTING NON-CDB TO PDB EXAMPLE 2 26
CONVERTING NON-CDB TO PDB EXAMPLE 3 27
OVERHEAD OF THE RM 28
• RM requires resources – I’ve heard rumors: 1-10% of CPU • Testing needed! NOTHING IS FOR FREE
MEASURING THE OVERHEAD HOW DO WE TEST? • HW – ODA V1 (12 Cores With HT => 24 Logical CPUs) – Two 6-core 3.06 GHz Intel Xeon® X5675 processors • Custom script – “Burns CPU” – Status checks • work done per session by consumer group • Response time of a non-DB script • Run 1 to 48 sessions in parallel • DB versions – 12.1.0.2 non-CDB – 12.1.0.2 CDB (tests executed in 1 PDB) – 11.2.0.4 30
TESTING SCRIPTS BURN_CPU.SQL -- parameter 1 is the thread number -- parameter 2 is the consumer_group name whenever sqlerror exit success rollback set ver off declare rnd number; i number; j number; r number; old_group varchar2(30); begin dbms_application_info.set_module('ORM_TEST','THREAD_'||&&1); dbms_random.seed('THREAD_'||&&1); rnd:=dbms_random.value*10000000+1; DBMS_SESSION.SWITCH_CURRENT_CONSUMER_GROUP('&&2', old_group, TRUE); DBMS_LOCK.sleep(5); for i in 0..1000000 loop for j in 0..1000000 loop r:=sqrt(sqrt(rnd*i*1000000+j+1)); dbms_application_info.set_client_info(i*1000000+j); end loop; end loop; end; / 31
TESTING SCRIPTS START_BURN.SH sqlplus -s rm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql sqlplus -s rm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql ... ... sqlplus -s rm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql sqlplus -s rm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql sqlplus -s rm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql wait 32
TESTING SCRIPTS STATUS.SQL DECLARE TYPE t_progr IS TABLE OF NUMBER INDEX BY VARCHAR2(64); pre_work t_progr; pre_sess t_progr; post_work t_progr; post_sess t_progr; pre_ts timestamp; post_ts timestamp; cursor c is select current_timestamp ts , nvl(RESOURCE_CONSUMER_GROUP,'{null}')||' / '||action RESOURCE_CONSUMER_GROUP, count(*) sessions, sum(CLIENT_INFO) WORK_DONE from v$session where module='ORM_TEST' group by current_timestamp, nvl(RESOURCE_CONSUMER_GROUP,'{null}')||' / '||action order by 2; c1 c%rowtype; c2 c%rowtype; l_key varchar2(100); work_done number; begin for c1 in c loop pre_ts:=c1.ts; pre_work(c1.RESOURCE_CONSUMER_GROUP):=c1.WORK_DONE; pre_sess(c1.RESOURCE_CONSUMER_GROUP):=c1.sessions; end loop; dbms_lock.sleep(30); for c2 in c loop post_ts:=c2.ts; post_work(c2.RESOURCE_CONSUMER_GROUP):=c2.WORK_DONE; post_sess(c2.RESOURCE_CONSUMER_GROUP):=c2.sessions; end loop; l_key := pre_work.first; LOOP EXIT WHEN l_key IS NULL; work_done:=round((post_work(l_key)-pre_work(l_key))/(extract(minute from (post_ts-pre_ts))*60+extract(second from (post_ts- pre_ts))),3); dbms_output.put_line(rpad(l_key,60,' ')||': '||rpad(post_work(l_key),16,' ')||' - '||rpad(pre_work(l_key),16,' ')||' = '||rpad(post_work(l_key)-pre_work(l_key)||' / '||(extract(minute from (post_ts-pre_ts))*60+extract(second from (post_ts- pre_ts)))||'s',40,' ')||' ==> '||work_done||' w/s (with '||post_sess(l_key)||' sessions) ' || (work_done/post_sess(l_key))||' w/s per session'); l_key := pre_work.next(l_key); END LOOP; end; / 33
TESTING SCRIPTS ! /USR/BIN/TIME ../RESPONSE.SH for i in {1..5000} do echo "sqrt($i)" | bc > /dev/null done 34
TEST1 NO RESOURCE MANAGER • Init parameters: – resource_limit=true – cpu_count=24 – resource_manager_plan='FORCE:’ • CDB – resource_manager_plan='FORCE:’ was set in all PDBs and ROOT. – ! Having a RM plan enabled in one PDB caused the whole CDB to be managed by the Resource Manager 35
TEST1 NO RESOURCE MANAGER 36 What’s  wrong   here?§ 12c  CDB  behaves  normally § Performance  degrades  starting  from  6-­7  parallel  sessions  on: -­ non-­CDB -­ 11gR2
TEST1 NO RESOURCE MANAGER 37 We’re  sleeping   for  Latch  Gets
TEST2 BURN_CPU.SQL V2 whenever sqlerror exit success rollback set ver off declare rnd number; i number; j number; r number; old_group varchar2(30); begin dbms_application_info.set_module('ORM_TEST','THREAD_'||&&1); dbms_random.seed('THREAD_'||&&1); rnd:=dbms_random.value*10000000+1; DBMS_SESSION.SWITCH_CURRENT_CONSUMER_GROUP('&&2', old_group, TRUE); DBMS_LOCK.sleep(5); for i in 0..1000000 loop for j in 0..1000000 loop r:=sqrt(sqrt(rnd*i*1000000+j+1)); if mod(j,1000)=0 then dbms_application_info.set_client_info(i*1000000+j); end if; end loop; end loop; end; / 38
TEST2 NO RESOURCE MANAGER – BURN_CPU.SQL V2 39 § 12c  CDB  shows  2x  higher  results  compared  to  TEST1  (it  didn’t  behave   normally!) § 11gR2  performs  worse  compared  to  12c
TEST2 NO RESOURCE MANAGER – BURN_CPU.SQL V2 40 § OS  script  response  is: -­ 5  – 9  s  for  1-­23  sessions -­ 70  – 90  s  for  24-­48  sessions  (14x  slower  )
TEST3 SIMPLE RESOURCE PLAN • The resource plan – SYS_GROUP = 1% at L1 – OTHER_GROUP = 1% at L1 – L2_GROUP1 = 1% at L1 • All sessions will be in L2_GROUP1 41
TEST3 SIMPLE RESOURCE PLAN 42 § Very  similar  results  to  TEST2  (no  RM)
TEST3 SIMPLE RESOURCE PLAN 43 § Even  a  very  simple  RM  plan  throttles  sessions  instead  of  letting  them   saturate  the  servers § Spike  at  exactly  24  active  sessions  is  caused  by  the  fact  the  RM  is  not  yet   throttling  sessions  and  all  Logical  CPUs  are  used What  is  that   spike?
TEST4 50% RESOURCE PLAN • The resource plan – SYS_GROUP = 5% at L1 – OTHER_GROUP = 45% at L1 – L2_GROUP1 = 50% at L1 • 1-18 sessions will be started in L2_GROUP1 • 19-60 sessions will be started in OTHER_GROUP • The Goal – Check if requested 50% are provided 44
TEST4 50% RESOURCE PLAN – 12C NON-CDB 45
TEST4 50% RESOURCE PLAN – 12C CDB 46 Why  am  I  not   Getting  my  50%   ? § I  forgot  to  set  the  RESORCE_MANAGER_PLAN  at  the  CDB  level
TEST4 50% RESOURCE PLAN – 12C CDB + FIXED THE RM SETTINGS 47 Now  it’s  all  much   better!
TEST4 50% RESOURCE PLAN – 11GR2 48
TEST5 ALLOCATION ACCURACY • The resource plan – SYS_GROUP = 1% at L1 – L2_GROUP1 = 10% at L1 – L2_GROUP2 = 20% at L1 – L2_GROUP3 = 30% at L1 – L2_GROUP4 = 39% at L1 – OTHER_GROUP = 0% at L1 • 24 sessions will be started in each group except SYS_GROUP • The Goal – Check if all percentages are met 49
TEST5 ALLOCATION ACCURACY – 12C NON-CDB 50
TEST5 ALLOCATION ACCURACY – 12C CDB 51
TEST5 ALLOCATION ACCURACY – 11GR2 52
RM OVERHEAD COMPARING AVG(W/S) FOR 24-48 SESSIONS TEST2/TEST3 53
FINDINGS 54
FINDINGS • The basic overhead of RM is negligible ( <1% ) – Outlier cases are possible (but rare) • Session holding a “latch” is sent off-CPU • Session holding a lock is sent off-CPU – .. only if out of resources already • OS Responsiveness is useful – For Troubleshooting – For keeping RAC alive • Don’t create “fancy” RM plans – It does not guarantee exact resource distribution – Tries its best on non-CDB and 11gR2 – Does it quite well on 12c CDB! • Careful with RM on CDB/PDBs! – Enabling it on 1 PDB enables it for the whole CDB – Remember the scheduler windows: (RMP='FORCE:')
? http://bit.ly/getMOSPatch elsins@pythian.com http://www.pythian.com/blog/author/elsins @MarisElsins 56

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DB12c: All You Need to Know About the Resource Manager

  • 1.
    DB12C: ALL YOUNEED TO KNOW ABOUT THE RESOURCE MANAGER Māris Elsiņš Lead Database Consultant Pythian @MarisElsins
  • 2.
    MARIS ELSINS Lead DatabaseConsultant at Pythian Oracle [Apps] DBA since 2005 Speaker at conferences since 2007 @MarisElsins elsins@pythian.com http://bit.ly/getMOSPatch
  • 3.
    ABOUT PYTHIAN 3 Founded  in 1997,  Pythian  is  a  global   leader  in  data  consulting  and  managed   services  specializing    in  planning,   optimizing,  and  managing  mission-­ critical  data  systems Top  5%  talent  worldwide     10  Oracle  ACEs 3  Oracle  ACE  Directors 18  years  in  business   450+  employees 250+  customers  worldwide  
  • 4.
    AGENDA • Features ofthe Resource Manager • The new 12c-stuff • Consolidations using Oracle Multitenant • Overhead of the RM 4
  • 5.
    FEATURES OF THERESOURCE MANAGER 5
  • 6.
    THE PROBLEM • OS doesn’t  care  enough  about  DB  sessions/processes   according  to  what  business  requires – Assigns  the  same  priority  to  all  processes – CPU  resources  are  equally  distributed  among  all  processes – Inability  to  manage  DB-­specific  resources/situations • CPU  distribution  among  sessions,  Parallel  Execution   Servers,  Active  session  Pool  and  Queuing,  Undo  usage,   Runaway  Queries,  Blocking  sessions – Context  switching  overhead  when  many  processes  running • Problems  start  when  there’s  not  enough  CPU  for   everyone • CPU  starvation  can  be  hard  to  recover  from (the  snowball  effect) • CPU  starvation  makes  online  troubleshooting  hard  to  do 6
  • 7.
    PROBLEM SCENARIOS -QUIZ TIME! • Running  reports  causes  too  much  load  on  the  OLTP  system. • One  of  the  sessions  allocate  all  parallel  query  slaves  therefore  other   sessions  don’t  get  any • Application  support  team  runs  heavy  queries  to  analyze  the  data   leaving  less  resources  for  online  transactions • Wide  search  criteria  cause  “hangs”  in  the  search  form • 3  of  8  CPU  cores  are  idle,  my  query  runs  without  parallel  execution,   I  could  use  the  idle  CPUs  to  provide  results  faster • Users  don’t  log  out  and  leave  idle  sessions • My  batch  process  requires  DOP=8  to  complete  in  time,  but  it’s   downgraded  to  smaller  DOP  if  enough  parallel  slaves  are  not  available • My  query  is  very  important.  It’s  IO  requests  have  to  be  prioritized! • Sessions  with  incomplete  transactions  have  locked  some  rows  and   other  sessions  have  stuck. 7
  • 8.
    THE BASIC CONCEPTS •Resource Manager – Included in Oracle EE license – Allows prioritization of sessions according to the defined business requirements – Allows defining the guaranteed amount of allocated resources for each type of sessions (consumer group) – Resources not used by higher priority sessions, can be used by lower priority sessions • Prioritizationis achieved by changing the process states to running/sleeping – DBRM / VKRM (CPU scheduling) – Semaphores (wake up sleeping processes) – CPU quantum (_dbrm_quantum) • Resource manager does not solve the «lack of CPU resources» problem, it just controls the execution queue • Resource manager uses some resources too, the last part of the presentation will estimate the overhead 8
  • 9.
    THE BASIC CONCEPTS 9 •Consumer group – Set of sessions having similar requirements for server resources – Resources are allocated to the consumer group, not individual sessions – DBA_RSRC_CONSUME_GROUPS • Directives – Rules that define resource allocation to the consumer group – DBA_RSRC_PLAN_DIRECTIVES • Resource plan – Set of directives defining the distribution of resources among consumer groups – DBA_RSRC_PLANS
  • 10.
    SQL> select event,count(*) from v$session group by event order by 2 desc; EVENT COUNT(*) ---------------------------------------------------------------- ---------- resmgr:cpu quantum 25 rdbms ipc message 23 Space Manager: slave idle wait 16 SQL*Net message from client 9 EMON slave idle wait 5 DIAG idle wait 2 LGWR worker group idle 2 GCR sleep 2 Streams AQ: waiting for time management or cleanup tasks 1 VKTM Logical Idle Wait 1 AQPC idle 1 Streams AQ: qmn coordinator idle wait 1 VKRM Idle 1 PING 1 ... 23 rows selected. RESMGR:CPU QUANTUM WHY IS MY SESSION NOT RUNNING? 10
  • 11.
    RESMGR:CPU QUANTUM WHY ISMY SESSION NOT RUNNING? SQL> select event, status, count(*) from v$session where event='resmgr:cpu quantum' group by event, status order by 1,2; EVENT STATUS COUNT(*) ------------------ -------- ---------- resmgr:cpu quantum ACTIVE 25 11
  • 12.
    RESMGR:CPU QUANTUM WHY ISMY SESSION NOT RUNNING? 12 SQL> select event, status, state, count(*) from v$session where event='resmgr:cpu quantum' group by event, status, state order by 1,2,3; EVENT STATUS STATE COUNT(*) ------------------ -------- ------------------- ---------- resmgr:cpu quantum ACTIVE WAITED KNOWN TIME 7 resmgr:cpu quantum ACTIVE WAITED SHORT TIME 16 resmgr:cpu quantum ACTIVE WAITING 2
  • 13.
    RESMGR:CPU QUANTUM WHY ISMY SESSION NOT RUNNING? • EVENT values are often misinterpreted in: – V$SESSION – V$SESSION_WAIT • Common mistake is to forget about v$session.STATE! • If STATE = 'WAITING’, only then the session is waiting – EVENT shows what the session is waiting for – STATUS can be ACTIVE or INACTIVE • If STATE = 'WAITED % TIME’ .. – and STATUS = 'ACTIVE', the session is ON CPU – and STATUS != 'ACTIVE', the session is not running THIS IS TRUE FOR ALL WAITEVENTS 13
  • 14.
    FEATURES 9.2 10.2 11.111.2 12.1 CPU resource allocation J J J J J Limit of the degree of parallelism J J J J J active session pool J J J J J Automated change of consumer group if session has used or is estimated to use the defined amount of resources CPU,   Est  CPU CPU,   Est  CPU CPU, Est CPU,   IO_MB,   IO_REQ CPU, Est CPU,   IO_MB,   IO_REQ CPU, Est  CPU,   IO_MB,   IO_REQ, LIO, Ela, Est  Ela Limit of estimated execution time J J J J J Limit size of undo used by uncommitted sessions J J J J J Termination of idle sessions J J J J Termination of idle blocking sessions J J J J L0 70% CPU _ORACLE_BACKGROUND_GROUP_ hidden consumer group for background processes J J J at  90% Instance caging /CPU_COUNT + resource plan/ J J Max CPU Utilization limit J J Parallel Statement Queue J J LOG_ONLY “switch group” for real-time SQL monitoring J Simplified automated consumer group switching J 14
  • 15.
  • 16.
    AUTOMATED CONSUMER GROUPSWITCHING 12C: MORE OPTIONS • Logical IO • Elapsed time • Estimated elapsed time • Real-time SQL monitoring – LOG_ONLY 16
  • 17.
    17 SELECT executions, end_of_fetch_count, elapsed_time/px_servers elapsed_time, cpu_time/px_servers cpu_time, buffer_gets /executions buffer_gets FROM (SELECT SUM(executions) AS executions, sum ( CASE WHEN px_servers_executions > 0 THEN px_servers_executions ELSE executions END) AS px_servers, SUM(end_of_fetch_count) AS end_of_fetch_count, SUM(elapsed_time) AS elapsed_time, SUM(cpu_time) AS cpu_time, SUM(buffer_gets) AS buffer_gets FROM gv$sql WHERE executions > 0 AND sql_id = :1 AND parsing_schema_name = :2 ) AUTOMATED CONSUMER GROUP SWITCHING ESTIMATED ELAPSED TIME
  • 18.
    AUTOMATED CONSUMER GROUPSWITCHING ESTIMATED ELAPSED TIME 18 SELECT executions, end_of_fetch_count, elapsed_time/px_servers elapsed_time, cpu_time /px_servers cpu_time, buffer_gets /executions buffer_gets FROM (SELECT SUM(executions_delta) AS EXECUTIONS, SUM( CASE WHEN px_servers_execs_delta > 0 THEN px_servers_execs_delta ELSE executions_delta END) AS px_servers, SUM(end_of_fetch_count_delta) AS end_of_fetch_count, SUM(elapsed_time_delta) AS ELAPSED_TIME, SUM(cpu_time_delta) AS CPU_TIME, SUM(buffer_gets_delta) AS BUFFER_GETS FROM DBA_HIST_SQLSTAT s, V$DATABASE d, DBA_HIST_SNAPSHOT sn WHERE s.dbid = d.dbid AND bitand(NVL(s.flag, 0), 1) = 0 AND sn.end_interval_time > (SELECT SYS imestamp at TIME ZONE dbtimezone FROM dual) - 7 AND s.sql_id = :1 AND s.snap_id = sn.snap_id AND s.instance_number = sn.instance_number AND s.dbid = sn.dbid AND parsing_schema_name = :2)
  • 19.
    REAL-TIME SQL MONITORINGIMPROVEMENTS LOG_ONLY – RESERVED CONSUMER GROUP NAME • Analyze the RM activity (V$SQL_MONITOR) – RM_LAST_ACTION – RM_LAST_ACTION_REASON – RM_LAST_ACTION_TIME – RM_CONSUMER_GROUP • Understand how and why the consumer groups are switched • V$SQL_MONITOR.QUEUING_TIME • The RM_% values are not presented in SQL Monitor reports or in EM 12c CC 19
  • 20.
    CONSUMER GROUP SWITCHING SIMPLIFIEDPRIVILEGES • In pre-12c any kind of switching required explicit privilege – DBMS_RESOURCE_MANAGER_PRIVS. GRANT_SWITCH_CONSUMER_GROUP • 12.1 privileges included for: – Consumer group mappings – Condition based on SWITCH_GROUP • What it means to DBAs? – Removes redundant work – Simplicity – More flexibility as explicit grants can be avoided 20
  • 21.
    CDB and PDBResource Plans CONSOLIDATION USING ORACLE MULTITENANT 21
  • 22.
    CDB RESOURCE PLAN •CDB resource plan – Defines how resources are distributed between PDBs – Shares – Minimum portion of resources allocated to the PDB – Additional Limits • Utilization_limit • Parallel_server_limit (%) • CDB Plan Directives (in DEFAULT_CDB_PLAN) – ORA$DEFAULT_PDB_DIRECTIVE – default • Shares=1, utilization_limit=100, parallel_server_limit=100 – ORA$AUTOTASK – for autotasks in root container • Shares=1, utilization_limit=90, parallel_server_limit=100 • User-defined directives for exceptional PDBs
  • 23.
    PDB RESOURCE PLAN •Allows to use the resources proportionally to the allocated shares • Works just like a resource plan for non-CDB • Few restrictions – A PDB resource plan can't have sub-plans. – A PDB resource plan can have a maximum of eight consumer groups. – A PDB resource plan cannot have a multi-level scheduling policy. • So we need to take action to re-implement the resource plans when we switch from non-CDB to the CDB? – Not always! It happens automatically, but how? 23
  • 24.
    CONVERTING NON-CDB PLANSTO PDB PLANS MULTI-LEVEL SCHEDULING POLICIES ARE NOT ALLOWER • Automatically when the non-CDB is converted into PDB – $ORACLE_HOME/rdbms/admin/noncdb_to_pdb.sql – The original plan and plan directivesare saved with STATUS=LEGACY – A new plan is added with the same name and STATUS={null} • Algorithm is not documented, but appears to be simple enough: – Adjust allocated CPU% on each level • Reduce each level to 75% proportionally • Leave it as is if it’s already lower than 75% – The “free portion” is passed to the lower level and split per calculated percentages, the remaining portion is passed down – The last level get’s all remaining resources 24
  • 25.
    CONVERTING NON-CDB TOPDB EXAMPLE 1 25
  • 26.
    CONVERTING NON-CDB TOPDB EXAMPLE 2 26
  • 27.
    CONVERTING NON-CDB TOPDB EXAMPLE 3 27
  • 28.
  • 29.
    • RM requiresresources – I’ve heard rumors: 1-10% of CPU • Testing needed! NOTHING IS FOR FREE
  • 30.
    MEASURING THE OVERHEAD HOWDO WE TEST? • HW – ODA V1 (12 Cores With HT => 24 Logical CPUs) – Two 6-core 3.06 GHz Intel Xeon® X5675 processors • Custom script – “Burns CPU” – Status checks • work done per session by consumer group • Response time of a non-DB script • Run 1 to 48 sessions in parallel • DB versions – 12.1.0.2 non-CDB – 12.1.0.2 CDB (tests executed in 1 PDB) – 11.2.0.4 30
  • 31.
    TESTING SCRIPTS BURN_CPU.SQL -- parameter1 is the thread number -- parameter 2 is the consumer_group name whenever sqlerror exit success rollback set ver off declare rnd number; i number; j number; r number; old_group varchar2(30); begin dbms_application_info.set_module('ORM_TEST','THREAD_'||&&1); dbms_random.seed('THREAD_'||&&1); rnd:=dbms_random.value*10000000+1; DBMS_SESSION.SWITCH_CURRENT_CONSUMER_GROUP('&&2', old_group, TRUE); DBMS_LOCK.sleep(5); for i in 0..1000000 loop for j in 0..1000000 loop r:=sqrt(sqrt(rnd*i*1000000+j+1)); dbms_application_info.set_client_info(i*1000000+j); end loop; end loop; end; / 31
  • 32.
    TESTING SCRIPTS START_BURN.SH sqlplus -srm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql sqlplus -s rm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql ... ... sqlplus -s rm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql sqlplus -s rm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql sqlplus -s rm/rm @burn_cpu.sql 1 L2_GROUP1 & sqlplus -s sys/asdasd as sysdba @../status.sql wait 32
  • 33.
    TESTING SCRIPTS STATUS.SQL DECLARE TYPE t_progrIS TABLE OF NUMBER INDEX BY VARCHAR2(64); pre_work t_progr; pre_sess t_progr; post_work t_progr; post_sess t_progr; pre_ts timestamp; post_ts timestamp; cursor c is select current_timestamp ts , nvl(RESOURCE_CONSUMER_GROUP,'{null}')||' / '||action RESOURCE_CONSUMER_GROUP, count(*) sessions, sum(CLIENT_INFO) WORK_DONE from v$session where module='ORM_TEST' group by current_timestamp, nvl(RESOURCE_CONSUMER_GROUP,'{null}')||' / '||action order by 2; c1 c%rowtype; c2 c%rowtype; l_key varchar2(100); work_done number; begin for c1 in c loop pre_ts:=c1.ts; pre_work(c1.RESOURCE_CONSUMER_GROUP):=c1.WORK_DONE; pre_sess(c1.RESOURCE_CONSUMER_GROUP):=c1.sessions; end loop; dbms_lock.sleep(30); for c2 in c loop post_ts:=c2.ts; post_work(c2.RESOURCE_CONSUMER_GROUP):=c2.WORK_DONE; post_sess(c2.RESOURCE_CONSUMER_GROUP):=c2.sessions; end loop; l_key := pre_work.first; LOOP EXIT WHEN l_key IS NULL; work_done:=round((post_work(l_key)-pre_work(l_key))/(extract(minute from (post_ts-pre_ts))*60+extract(second from (post_ts- pre_ts))),3); dbms_output.put_line(rpad(l_key,60,' ')||': '||rpad(post_work(l_key),16,' ')||' - '||rpad(pre_work(l_key),16,' ')||' = '||rpad(post_work(l_key)-pre_work(l_key)||' / '||(extract(minute from (post_ts-pre_ts))*60+extract(second from (post_ts- pre_ts)))||'s',40,' ')||' ==> '||work_done||' w/s (with '||post_sess(l_key)||' sessions) ' || (work_done/post_sess(l_key))||' w/s per session'); l_key := pre_work.next(l_key); END LOOP; end; / 33
  • 34.
    TESTING SCRIPTS ! /USR/BIN/TIME../RESPONSE.SH for i in {1..5000} do echo "sqrt($i)" | bc > /dev/null done 34
  • 35.
    TEST1 NO RESOURCE MANAGER •Init parameters: – resource_limit=true – cpu_count=24 – resource_manager_plan='FORCE:’ • CDB – resource_manager_plan='FORCE:’ was set in all PDBs and ROOT. – ! Having a RM plan enabled in one PDB caused the whole CDB to be managed by the Resource Manager 35
  • 36.
    TEST1 NO RESOURCE MANAGER 36 What’s wrong   here?§ 12c  CDB  behaves  normally § Performance  degrades  starting  from  6-­7  parallel  sessions  on: -­ non-­CDB -­ 11gR2
  • 37.
    TEST1 NO RESOURCE MANAGER 37 We’re sleeping   for  Latch  Gets
  • 38.
    TEST2 BURN_CPU.SQL V2 whenever sqlerrorexit success rollback set ver off declare rnd number; i number; j number; r number; old_group varchar2(30); begin dbms_application_info.set_module('ORM_TEST','THREAD_'||&&1); dbms_random.seed('THREAD_'||&&1); rnd:=dbms_random.value*10000000+1; DBMS_SESSION.SWITCH_CURRENT_CONSUMER_GROUP('&&2', old_group, TRUE); DBMS_LOCK.sleep(5); for i in 0..1000000 loop for j in 0..1000000 loop r:=sqrt(sqrt(rnd*i*1000000+j+1)); if mod(j,1000)=0 then dbms_application_info.set_client_info(i*1000000+j); end if; end loop; end loop; end; / 38
  • 39.
    TEST2 NO RESOURCE MANAGER– BURN_CPU.SQL V2 39 § 12c  CDB  shows  2x  higher  results  compared  to  TEST1  (it  didn’t  behave   normally!) § 11gR2  performs  worse  compared  to  12c
  • 40.
    TEST2 NO RESOURCE MANAGER– BURN_CPU.SQL V2 40 § OS  script  response  is: -­ 5  – 9  s  for  1-­23  sessions -­ 70  – 90  s  for  24-­48  sessions  (14x  slower  )
  • 41.
    TEST3 SIMPLE RESOURCE PLAN •The resource plan – SYS_GROUP = 1% at L1 – OTHER_GROUP = 1% at L1 – L2_GROUP1 = 1% at L1 • All sessions will be in L2_GROUP1 41
  • 42.
    TEST3 SIMPLE RESOURCE PLAN 42 §Very  similar  results  to  TEST2  (no  RM)
  • 43.
    TEST3 SIMPLE RESOURCE PLAN 43 §Even  a  very  simple  RM  plan  throttles  sessions  instead  of  letting  them   saturate  the  servers § Spike  at  exactly  24  active  sessions  is  caused  by  the  fact  the  RM  is  not  yet   throttling  sessions  and  all  Logical  CPUs  are  used What  is  that   spike?
  • 44.
    TEST4 50% RESOURCE PLAN •The resource plan – SYS_GROUP = 5% at L1 – OTHER_GROUP = 45% at L1 – L2_GROUP1 = 50% at L1 • 1-18 sessions will be started in L2_GROUP1 • 19-60 sessions will be started in OTHER_GROUP • The Goal – Check if requested 50% are provided 44
  • 45.
    TEST4 50% RESOURCE PLAN– 12C NON-CDB 45
  • 46.
    TEST4 50% RESOURCE PLAN– 12C CDB 46 Why  am  I  not   Getting  my  50%   ? § I  forgot  to  set  the  RESORCE_MANAGER_PLAN  at  the  CDB  level
  • 47.
    TEST4 50% RESOURCE PLAN– 12C CDB + FIXED THE RM SETTINGS 47 Now  it’s  all  much   better!
  • 48.
  • 49.
    TEST5 ALLOCATION ACCURACY • Theresource plan – SYS_GROUP = 1% at L1 – L2_GROUP1 = 10% at L1 – L2_GROUP2 = 20% at L1 – L2_GROUP3 = 30% at L1 – L2_GROUP4 = 39% at L1 – OTHER_GROUP = 0% at L1 • 24 sessions will be started in each group except SYS_GROUP • The Goal – Check if all percentages are met 49
  • 50.
  • 51.
  • 52.
  • 53.
    RM OVERHEAD COMPARING AVG(W/S)FOR 24-48 SESSIONS TEST2/TEST3 53
  • 54.
  • 55.
    FINDINGS • The basicoverhead of RM is negligible ( <1% ) – Outlier cases are possible (but rare) • Session holding a “latch” is sent off-CPU • Session holding a lock is sent off-CPU – .. only if out of resources already • OS Responsiveness is useful – For Troubleshooting – For keeping RAC alive • Don’t create “fancy” RM plans – It does not guarantee exact resource distribution – Tries its best on non-CDB and 11gR2 – Does it quite well on 12c CDB! • Careful with RM on CDB/PDBs! – Enabling it on 1 PDB enables it for the whole CDB – Remember the scheduler windows: (RMP='FORCE:')
  • 56.