Which new Oracle 9i features are helpful for a SAP customer?

Which new Oracle 9i features are helpful for a SAP customer?
Dr. Stephan Bühne Oracle SAP Solution Center Walldorf

Initialisation: spfile vs. Pfile
SGA: Dynamic Resizing Multiple Block Size Support PGA: Automatic Memory Management Automatic UNDO Management Resumable Space Allocations Identifying unused indexes Online-Reorganisation

Initialisation: spfile vs. pfile
Spfile replaces traditional init.ora file Allows server to maintain parameter settings All members of RAC can use the same file Is maintained by the oracle server

Binary file Is created with the command: „Create spfile from pfile;“ Alter system set parameter = value scope = Memory | Spfile | Both Example: Alter system set SORT_AREA_SIZE = comment ´Temporary Change´ scope = spfile;

Exporting spfile: „Create pfile from spfile;“ *.sort_area_size= #Temporary change prd1. shared_pool_size=200m prd2. shared_pool_size=150m *.sessions=200

Dynamic SGA Oracle 8i Buffer Cache and Shared Pool are fixed
Recycle Pool and Keep Pool are defined out of all DB_Block_Buffers

Shared_Pool_Reserved_Size
SGA Oracle 8i Shared Pool Shared_Pool_Reserved_Size SHARED_POOL_RESERVED_SIZE SHARED_POOL_SIZE = Default Buffer Pool DB_BLOCK_BUFFERS = Recycle BUFFER_POOL_RECYCLE Keep BUFFER_POOL_KEEP

Dynamic SGA Oracle 9i Buffer Cache and Shared Pool can be dynamically changed No database restart necessary

Shared_Pool_Reserved_Size
SGA Oracle 9i SGA_MAX_SIZE = 2048M Shared Pool Shared_Pool_Reserved_Size SHARED_POOL_SIZE Keep DB_KEEP_CACHE_SIZE Recycle DB_RECYCLE_CACHE_SIZE Default DB_CACHE_SIZE

Dynamic SGA: Parameters
If you want make use of the dynamic SGA resizing you MUST use new parameters: DB_CACHE_SIZE (DB_BLOCK_BUFFERS) DB_KEEP_CACHE_SIZE (BUFFER_POOL_KEEP) DB_RECYCLE_CACHE_SIZE (BUFFER_POOL_RECYCLE)

Dynamic SGA: MONITORING
Efficieny of the buffer cache can be monitored with View V$DB_CACHE_ADVICE Parameter DB_CACHE_ADVICE must be specified OFF: Advisory is turned off ON: Advisory is turned on READY: Advisory is turned off, but needed memory is allocated

Dynamic SGA: V$DB_CACHE_ADVICE
Cache Size (MB) Buffers Estd. Read Factor Physical Reads 30 3,802 18.70 192,317,943 60 7,604 12.83 131,949,536 91 11,406 7.38 75,865,861 ... 304 38,020 1.00 10,282,475 334 41,822 .93 9 ,515,878 364 45,624 .87 8,909,026 608 76,040 .66 6,739,731 10 % 20 % 30 % 100 % 110 % 120 % 200 %

Dynamic SGA: Summary MAX_SGA_SIZE specifies the total amount of memory used for the oracle SGA Within this specified size all parts of the SGA can be resized dynamically KEEP and RECYCLE Buffers are specified additionally More flexibility to adjust SGA to the current needs

Dynamic SGA: Summary View V$DB_CACHE_ADVICE can be used to estimate optimal buffer cache size Feature can be switched on/ off dynamically Partial analysis for specific workload is possible Dynamic SGA Resize is also possible in RAC environments

Multiple Block Sizes Tablespaces within one database can have different Oracle Block Sizes Is setup on Tablespace creation Up to five different Sizes can be used Supported Block Sizes: 2k, 4k, 8k, 16k, 32k Each block size has an own buffer cache area

Multiple Block Sizes SGA_MAX_SIZE = 2048M DB_CACHE_SIZE = 16K
Keep DB_KEEP_CACHE_SIZE Recycle DB_RECYCLE_CACHE_SIZE Default Block Size = 8k DB_CACHE_SIZE

Multiple Block Sizes: Monitoring
View V$BUFFER_POOL displays information about specified buffer pools Block Size Current Size Buffers Target Size Prev. Size 4096 32 7868 48 2048 16 7570 16384 1013

Multiple Block Sizes: Summary
A separate Buffer cache must exist, before a tablespace can be created System TS and Temp TS must have default blocksize Larger block sizes are useful for tables containing Long Raw fields BW-Application can benefit (FTS) Useful for SAP Cluster or Pool Tables

Automatic PGA Management
Simplifies and improves memory allocation SQL working areas can be adjusted automatically and dynamically Ease of memory tuning Reduction of time to tune memory Better throughput Improved query response time

Untunable Memory Tunable Memory SORT_AREA_SIZE HASH_AREA_SIZE BITMAP_MERGE_AREA_SIZE CREATE_BITMAP_AREA_SIZE Process Code Heap Memory Untunable Memory Tunable Memory Process PGA Untunable Memory Tunable Memory Process PGA Untunable Memory Tunable Memory Process PGA Untunable Memory + Tunable Memory <= PGA_AGGREGATE_TARGET

Automatic PGA Management: Standard R/3
Tunable Memory Untunable Memory = SORT_AREA_SIZE Process PGA Process PGA Process PGA Process PGA 95 % + 5 % <= PGA_AGGREGATE_TARGET

Automatic PGA Management: BW R/3
SORT_AREA_SIZE HASH_AREA_SIZE BITMAP_MERGE_AREA_SIZE CREATE_BITMAP_AREA_SIZE Tunable Memory Untunable Memory Process PGA Process PGA Process PGA Process PGA 5 % + 95 % <= PGA_AGGREGATE_TARGET

New Oracle Parameters introduced: PGA_AGGREGATE_TARGET 10 MB – 400 GB WORKAREA_SIZE_POLICY MANUAL (Default) AUTO (Default if PGA_AGGREGATE_TARGET is set)

The AUTO Mode ensures: The overall size of the PGA memory never exceed PGA_AGGREGATE_TARGET A Single process never runs out of memory

PGA Management: Monitoring
New Statistics in V$SYSSTAT: Name Value work area memory allocated (KB) Work area executions – optimal size 2683 Work area executions – one pass size 153 Work area executions –multipasses size 10

V$SYSSTAT WORK_AREA_MEMORY_ALLOCATED Total amount of PGA allocated either by a single process or overall WORK_AREA_EXECUTIONS_OPTIMAL Optimal size: No write to disk necessary WORK_AREA_EXECUTIONS One Pass Query could executed with a single disk pass WORK_AREA_EXECUTIONS MULTIPASS Multiple pass runs were necessary

PGA Management: Monitoring
New View V$PGASTAT: Name Value aggregate PGA auto target global memory bound total expected memory total PGA inuse total PGA allocated maximum PGA allocated total PGA used for auto workareas 939008 maximum PGA used for auto workareas total PGA used for manual workareas maximum PGA used for manual workareas estimated PGA memory for optimal maximum PGA memory for optimal estimated PGA memory for one-pass maximum PGA memory for one-pass

Automatic UNDO Management
Simplifies management of undo data No reasons for create, drop, alter rollback segments UNDO segments can be managed either manual or automatic Data is managed by a single UNDO-tablespace

System TBS UNDO TBS _SYSSMU1$ Auto System Rollback Segment _SYSSMU2$ _SYSSMUn$ System TBS RBS TBS RBS1 Manual System Rollback Segment RBS2 RBSn

UNDO_MANAGEMENT Switches automatic UNDO management on/off UNDO_TABLESPACE Defines which automatic UNDO tablespace is used UNDO_SUPPRESS_ERRORS Supresses errors if invalid UNDO command is issued UNDO_RETENTION Specifies the time in seconds Read Consistency should be guarenteed

UNDO Management Monitoring
V$UNDOSTAT Displays the UNDO usage in 10 Minutes intervals Begin_Time End_Time UNDOBLKS TXNCOUNT MAXCON :01 :11 135 36 3 :21 255 55 6 :31 198 48 4 .... Undo space = (UR x UPS) + Overhead UR = Undo Retention Parameter UPS = Undo Blocks per second

Resumable Space Allocation
Resumable operation are suspended under „Out of space“-errors (e.g. ORA-1653, ORA-1631, ORA-1562, ORA-1628, ...) A session running in one of these error conditions is not aborted, but waits for a specified amount of time to proceed

Resumable space operation is enabled Transaction starts Out-Of Space error occurs Error is written to alert.log Error is fixed (e.g. Datafile added) Suspended operation resumes automatically Operation ends successfully

But: Must be activated on session level „Alter session enable resumable timeout nn“ ; How to activate in SAP environments ?

But: Must be activated on session level „Alter session enable resumable timeout nn“ ; How to activate in SAP environments ? => Logon Trigger

Logon Trigger: CREATE OR REPLACE TRIGGER RESUMABLE_TRANSACTION after logon on SAPR3.SCHEMA BEGIN execute immediate ´alter session enable resumable timeout 14400´; END; / Must be created with SYDBA privileg Can be enabled/ disabled as needed

Resumable statements are: Queries (Sort Area, Hash Area) DML statements (max. Extents, TBS full, Rollback) SQL*Loader operations Import and Export operations DDL statements (Create Index, Index rebuild, CTAS) Status can be monitored with DBA_RESUMABLE

DBA_RESUMABLE: Session Status TIMEOUT START_TIME SUSPEND_TIME 7 NORMAL 14400 11/12/02 00:03:59

Identifying Unused Indexes
Monitoring is done during Parse Time Helps to identify unused indexes in the system to save space and resources Only Parsing Step is monitored, not the execution

Alter index <name> monitoring usage Switches Monitoring on for the specified index Alter index <name> nomonitoring usage Switches Monitoring off for the specified index Switching monitoring ON/ OFF forces reparsing on all SQl statements on the table

A new DBA View V$OBJECT_USAGE exists to view the monitoring results: Index Name Table Name Mon Usage Start End MSEG~Z01 MSEG YES NO 14:37:00 08:14:00 MSEG~Y01 14:37:05 08:14:01

Online Reorganisation
Tables can be converted: Non-Partitioned  Partitioned Columns can be dropped Columns can be renamed New Columns can be added LOB are supported B UT: Long Raw fields are not supported

Source Table Result Table Transform Transform Updates Store Updates

For the reorganisation the following steps must be performed: Dbms_redefinition.can_redef_table (´Owner´, ´Table´); PL/SQL procedure successfully completed ORA cannot online redefine table with no primary key An error is reported, if the table can not be online reorganized. Please note: For tables with Long Raw field no error is reported!

A Primary Key must be created on the table. Alter table SAPR3.MSEG add Primary Key (MANDT,.....) Enable Novalidate;

A Temporary object must be created, having the same attributes as the source table. You can use sapdba to create the correct table syntax or directly SQL e.g.: Create table SAPR3.MSEG_TEMP Tablespace PSAPMSEGD AS Select * from SAPR3.MSEG Where 1 = 0;

Save the Default Constraints from the existing table be either using sapdba or by using exp/imp command. Export table without data Import with option indexfile=<name> Use resulting File to recreate Default constraints later

Run the PL/ SQL Procedure to start Redefinition: Exec Dbms_redefinition.start_redef_table (´SAPR3´,´MSEG´,´MSEG_TEMP´);

Create all indexes on the Temporary Table with different names with the same definition as they exist on the Original table Create Index SAPR3.“MSEG~M_TEMP“ On SAPR3.MSEG_TEMP (MANDT, ...) Tablespace PSAPMSEGI

To synchronize tables Run intermediate Exec Dbms_redefinition.sync_interim_table (´SAPR3´,´MSEG´,´MSEG_TEMP´);

To finish synchronize tables Run Exec Dbms_redefinition.finish_redef_table (´SAPR3´,´MSEG´,´MSEG_TEMP´);

Apply the Default constraints on the new table if needed If an abort is needed, you MUST call the procedure dbms_redefinition.abort_redef_table (´SAPR3´,´MSEG´,´MSEG_TEMP´)

Prerequisites: Table must have Primary Key ! Must Not have Long Raw fields LOB are supported

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