Peter Ramm's Oracle performance analysis stuff

A sensitive issue for DBAs and developers is often the detection and removal of indexes in Oracle databases that are not or no longer needed. In practice systems can be found that allocate more than 50% of the storage with indexes without any productive relevance. Nevertheless, this potential for a simple reduction of storage requirements and system load is regularly not used, freely after "never touch a running system" or "why should I burn my fingers here and then this index is still needed somewhere". This article demonstrates how to securely determine irrelevant indexes using the freely available analysis tool " Panorama ". Why define indexes on tables Optimizing accesses from User-SQL - Reduction of access to the result-relevant records when reading table data Guarantee of uniqueness - Declaration of unique indexes or use of the index for primary key or unique constraints Protection of Foreign Key Constraints - Preventing full table scans w...

Partition Exchange requires a partitioned and a non-partitioned table with the same column and index structure. All indexes of the partitioned table have to be local partitioned. The following SQL lists all combinations of structure-identical partitioned and non-partitioned tables that are suitable for partition exchange. This information may be useful before changing the structure of tables or indexes to be informed about possible partition exchange operation and to prevent from crashing such operations. WITH Tables AS (SELECT /*+ NO_MERGE MATERIALIZE */ tc.Owner, tc.Table_Name, COUNT(*) Columns, SUM(ORA_HASH(tc.Data_Type) * tc.Column_ID * tc.Data_Length * NVL(tc.Data_Precision,1) * NVL(DECODE(tc.Data_Scale, 0, -1, tc.Data_Scale),1)) Structure_Hash FROM DBA_Tab_Columns tc JOIN DBA_Tables t ON t.Owner = tc.Owner AND t.Table_Name = tc.Table_Name /* exclude views */ ...

Panorama is now able to connect to autonomous databases in the Oracle cloud. At start of Panorama you must ensure that environment variable TNS_ADMIN targets to a directory containing: the tnsnames.ora provided by Oracle cloud the unzipped files from the Oracle wallet provided by Oracle cloud: Oracle wallet files (ewallet.sso, ewallet.p12)  Java KeyStore (JKS) files (truststore.jks, keystore.jks). Connection properties required to use Oracle Wallets or Java KeyStore (ojdbc.properties)

Starting with Release 12.2 of Oracle database you can list and view trace files from database server file system by SQL selects. Dynamic performance views for representation of trace files are: V$DIAG_TRACE_FILE: lists files from ADR (automatic diagnostic repository) V$DIAG_TRACE_FILE_CONTENTS: lists text content of trace files with one record per line Panorama now supports viewing server side trace files via menu "DBA general" / "Server Files" / "Server Trace Files". This way people without access rights on database server file systems (like software developer) are enabled to access the trace files they produce by their own. This view shows all existing trace files for chosen period and optional including or excluding patterns for trace file name. This works for server trace files as well as for user trace files created by: ALTER SESSION SET SQL_TRACE=TRUE; or ALTER SESSION SET EVENTS '10046 trace name context forever, level 4|8|12'...

Knowing that Oracle-DB does not automatically release storage below the high water mark it would be necessary to do it yourself. Usually you may scan your database from time to time to identify tables, indexes or lobs where reorganization of these objects can make significant amount of storage in tablespace available for other objects. The PL/SQL package DBMS_SPACE allows consideration of free space in DB blocks for an object. This information can be used to forecast the effect of object reorganization. Unfortunately DBMS_SPACE.Space_Usage takes longer time for evaluation of larger objects, so it is quite expensive to scan a whole schema or system using DBMS_SPACE. Following I'll show how the performance analysis tool Panorama  handles determining candidates for reorganization. To determine candidates for deeper inspection Panorama uses a simple calculation based on avg. row-length, Pct_Free and Ini_Trans to list suspected objects that are worth to reorganize. Sorting th...

Unfortunately, dynamic remastering in RAC clusters has very little official documentation. Some useful information about this topic you may get here: http://oracleinaction.com/dynamic-remastering/ https://www.hhutzler.de/blog/a-closer-look-into-drm-dynamic-resource-management/ https://orainternals.wordpress.com/2010/03/25/rac-object-remastering-dynamic-remastering/ As part of the performance analysis app  Panorama you can view the instance-affinity of tables, indexes and their partitions as well as the history of DRM events per object or globally. The history info is gotten from view gv$Policy_History. The current affinity comes from view V$GCSPFMaster_Info. The object detail view shows you the master instance of each object like here for a table: Click on instance number list the complete history of DRM events for this object: In addition you can also get an overview over all DRM actions of your database. Starting with menu "Analyses/Stat...

The Oracle performance analysis app Panorama as Docker container does not natively support https-connections. But securing http-access to Panorama can easily be reached by running the Panorama-container behind a reverse proxy. This example shows using Nginx as reverse proxy and docker-compose to place Panorama behind the reverse proxy. I've used already existing own SSL-certificates for the target host. Obviously you may want to use certificates generated by Lets Encrypt  but this often doesn't work in company environments behind firewalls. Place the pem- and key-file of your certificate combined with the two files "docker-compose.yml" and "nginx.conf" in one directory and run "docker-compose up" to start Panorama and Nginx. Example for nginx.conf (replace certificate file names): # Nginx config for Panorama # Peter Ramm, 22.03.2019 events { } http { # Redirect all http traffic on port 80 to https 443 server { listen 80 def...

Starting with release 12.1 the Enterprise Manager Express of Oracle-DB contains an aggregated view of performance metrics called "Performance Hub". Panorama , the free tool for performance analysis on Oracle-DB now also includes this Performance-Hub report. You may call the Performance Hub report by menu "Analysis / Statistics" / "Genuine Oracle AWR-reports" / "Performance Hub". After setting start and end date and optional RAC-instance the Performance Hub report opens in a discrete browser tab (if you allow Adobe Flash to execute). The DB-user used for connecting Panorama to the database needs the role EM_EXPRESS_BASIC or DBA to be able to call the Performance Hub report.

Update 2023-05:  Checked the above issues against Rel. 19.18 It works much better now than before in Rel. 12.x.  Not completely without the risk of getting migrated rows and not deterministic at all. But with much smaller amount of situations resulting in increasing storage footprint and migrated rows.

Starting with release 10.1 Oracle introduced automatic shared memory management. Setting only SGA_TARGET=x without defining limits for the SGA-components (buffer cache, shared pool, large pool, java pool) allows your database to redistribute SGA memory between components due to current needs. This will work properly in many cases but sometimes there are some pitfalls: A very common problem on Oracle databases are applications without usage of bind variables in their SQL statements. Not using bind variables leads to excessive SGA memory consumption in shared pool and parse effort if you have a large number of SQLs executed with different values in filter conditions stored as literals. For example: SELECT a, b FROM Item WHERE ItemNo = 453612; SELECT a, b FROM Item WHERE ItemNo = 876886; etc. instead of SELECT a, b FROM Item WHERE ItemNo = :ItemNo; In such a situation the DB may resize the SGA. The size of the shared pool will grow thus reducing the size of the buffer cache...

SQL-Monitoring records individual executions of an SQL statement in detail if they fulfill one of the following prerequisites: Execution with parallel query CPU- or I/O-activity for more than 5 seconds Optimizer-hint `MONITOR` in SQL statement SQL-Monitoring reports are stored in table v$SQL_Monitor during SQL execution and for a very short period after execution. The precondition for using the monitoring reports is licensing of the Tuning Pack for the Enterprise Edition. Starting with Oracle 12.1, the short-living detailed monitoring reports from v$SQL_Monitor are also available for a longer time within the AWR retention period via DBA_Hist_Reports and DBA_Hist_Reports_Details. This report can be exported as HTML-page which uses Adobe-Flash to render the Database Activity Report for this SQL execution similar to Enterprise manager. To generate the HTML-report from v$SQL_Monitor call: SELECT DBMS_SQLTUNE.report_sql_monitor( ...

Long time ago Oracle introduced SQL patches as a way to influence execution plan of SQL with optimizer hints without changing the original SQL statement. This allows fixing execution plan issues without any change at the application executing this SQL. SQL patches don't require additional license in contrast to SQL plan baselines and SQL profiles and can also be used with Standard Edition. SQL patches are normally used in workflow of SQL Repair Advisor but can also be created manually. There are two variants to create a SQL patch for a SQL: By SQL-ID and by SQL text. (See also this posts: 1   2  ) I personally prefer SQL patch creation using SQL text because SQL-ID requires existence of SQL-Statement in SGA at SQL patch creation time. For Oracle 11.1 .. 12.1 create with package-method sys.DBMS_SQLDiag_Internal.i_create_patch BEGIN sys.DBMS_SQLDiag_Internal.i_create_patch( sql_text => 'SELECT SYSDATE FROM DUAL', hint_text => 'PARALLEL(8)...

This post describes how Panorama allows usage without violating Oracle's license conditions if you don't have Diagnostics Pack and Tuning Pack license. You can run Panorama with access on original AWR/ASH (which requires EE and Diagnostics Pack) or with access on Panorama's own sampled history data which doesn't require EE and Diagnostics Pack. Before accessing AWR/ASH-data Panorama asks you which mode you want to use. Several functions of Panorama require one of the following: Enterprise Edition and Diagnostics Pack licensed or Use Panorama's own data sampled by Panorama-Sampler instead Panorama's function "SQL monitor" is available only if you've licensed Oracle's "Tuning Pack". Accessing restricted dictionary data (like AWR) with Panorama has preconditions to ensure compliance with Oracle's license conditions: After connecting to a database with Panorama you have to acknowledge at first one of the four options:...

Panorama is my free performance analysis tool for Oracle-DB. From now it offers it's own database workload recording 'Panorama-Sampler' as alternative to use of Oracle's origin AWR and ASH data. This enables you to use Panorama's functions for evaluation of historic workload info: with any database edition including Standard Edition without licensing of Diagnostics Pack for Enterprise Edition In addition to Oracle's AWR Panorama-Sampler may also record historic information for: Size evolution of tablespace objects Usage of DB-cache by objects Detailed info for blocking lock scenarios You may find more about Panorama and it's sampling feature including download link at: http://rammpeter.github.io/panorama_sampler.html http://rammpeter.github.io/panorama.html

A common pitfall while using sequences in Oracle-DB is forgetting to define sequence caching. The default for sequences is cache size = 0. That means, every sequence.nextval operation triggers a single write operation on dictionary table sys.SEQ$. Especially if frequently calling sequence.nextval uncached sequences may cause significant performance degradation. Frequently calling sequence.nextval in parallel sessions may lead to ramdom lock scenarios in library cache. Setting a cache size for a sequence may heavy increase performance of nextval-operations. There's a minimal memory overhead for caching a sequence because all that's needed is a counter to increase in SGA memory and a upper limit. If this limit is reached with the counter, the upper limit is increased by cache size and the new upper limit is written down once to SEQ$. The possible drawback for sequence caching is that you loose all your values between the current value and the highest cached value if yo...

A common problem with indexes is: creating an index is quite easy in consideration of the possible impact deleting an index is much more difficult because: Who has the heart to decide this index is really no longer needed?  This results in: Nearly every database system stores and maintains indexes that are not really needed. In worst cases this not needed indexes are more than half of the systems total storage Securely indentifying and deleting this unnecessary indexes may be a strong lever to improve performance and reduce resource consumption without any changes on application. How to identify unused indexes: 1. Use Oracle's own index usage monitoring  You can enable index usage monitoring by issueing  ALTER INDEX <Index_Name> MONITORING USAGE; Index usage is expressed as YES/NO-state that flips to YES if index is used by any executed SQL-statement. Combined with start monitoring timestamp you can identify indexes that are not used by SQL si...