Blog Archives

What to do if a database performance issue is reported

A high level overview. Expectation should be for all OLTP operations to take less than 1 second, and all batch processing jobs and background scheduled report jobs to take less than 1 hour each. This is deliverable on even large

Posted in Performance tuning

Rman list most recent backups

List most recent rman database backups on target database sqlplus with: set pages 9999 lines 132 ALTER SESSION SET nls_date_format = ‘Dy DD-Mon-YYYY HH24:MI:SS’ ; SELECT b.checkpoint_time , b.incremental_level , COUNT(*) FROM v$backup_datafile b JOIN v$datafile f ON f.file# =

Posted in Rman

Oracle hint cursor_sharing_exact using sql patch

Bind variable peeking is still a cause of plan instability, even after 11gR1’s introduction of adaptive cursor sharing. In my case adaptive cursor sharing wasn’t helpful for a daily batch job, because the sql was aged out of cache by

Posted in Performance tuning

Oracle select earliest and latest rows using keep group or first_value analytics

There are two ways of selecting the earliest and latest rows for each customer. 1) Keep group: SELECT t1.customer_ref , MAX ( t1.order_amount ) KEEP ( DENSE_RANK FIRST ORDER BY t1.order_date ASC ) AS earliest_order_amount , MAX ( t1.order_amount )

Posted in Uncategorized

Windows PowerShell run script on all SQL Servers recovery mode

Micrsoft SQL Server databases should be kept in full recovery mode (the equivalent of Oracle’s archivelog mode) except for the master, tempdb, ReportServerTempDB databases. To check all databases in a SQL Server instance, run the below script in a SQL

Posted in SQL server, Uncategorized

Oracle Full Text simple example for like % grep wildcard

The equivalent of the grep command in oracle is like: SELECT * FROM dba_source s WHERE LOWER ( s.text ) LIKE ‘%within group%’ ; That works fast enough for querying dba_source, which is a small dataset. But for even medium

Posted in Performance tuning

Oracle top session info in RAC with tracefile name

See real time top session info in either RAC or standalone database, including tracefile name qualified by instance name, with: — ALTER SESSION SET nls_date_format = ‘Dy DD-Mon-YYYY HH24:MI:SS’ ; SELECT DISTINCT s.inst_id , s.sid , s.serial# , s.username ,

Posted in Performance tuning, Uncategorized

10046 trace a module using logon trigger

1) Update – thanks to Joaquin Gonzalez for pointing out a preferable safer method than logon trigger for 10046 tracing a particular module: EXEC DBMS_MONITOR.serv_mod_act_stat_enable ( service_name => ‘myservice’ , module_name => ‘myModule.exe’ , binds => TRUE ) You can

Posted in Performance tuning

mtputty directory path title

MtPuTTY multi tabbed putty is an improved variant of putty ssh client, easier to use if working on several servers at the same time. However it has an annoying tendency to display long directory paths in each tab title. You

Posted in Uncategorized

Oracle date changed user changed columns and batch performance

Most core application tables benefit from columns like these: ALTER TABLE mytable ADD ( date_created DATE DEFAULT SYSDATE , user_created_by VARCHAR2(30) DEFAULT USER , date_changed DATE , user_changed_by VARCHAR2(30) ) ; The default values deal with inserts, for updates a

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