Tips and tricks for optimal application performance using Oracle databases.
Especially usage and functions of my Swiss army knife "Panorama" for Oracle performance analysis are explained.
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...
It's very common that firewalls are terminating idle TCP sessions after a limited time, often after approximately one hour. Possible problem If you have a long running SQL or PL/SQL program and the firewall terminates your apparently idle TCP session this may lead to the following scenario: the database is not able to send result to client. After reaching the TCP-timeout the database server terminates the DB-Session the client program stays in socket read forever waiting for the database response Oracle's full solution: SQLNET.EXPIRE_TIME=x in sqlnet.ora Oracle's solution for this problem is setting parameter SQLNET.EXPIRE_TIME=x in sqlnet.ora where x are the minutes between keep alive packets on idle sessions that inform the firewall that this session is always alive. SQLNET.EXPIRE_TIME hast to be set in the sqlnet.ora of your RDBMS' ORACLE_HOME. Normally $ORACLE_HOME/network/admin. If you have a grid infrastructure setting SQLNET.EXPIRE_TIME in sqlnet...
One of the new features backported from 23ai into release 19.28 is the SQL Diagnostic Report. This shows a comprehensive summary of diagnostic information for a certain SQL statement. Included are execution plan info, optimizer statistics, object info, ASH info, SQL Monitor reports and lots more. The documentation for 19c already includes the new method DBMS_SQLDIAG.Report_SQL . Which edition or option pack license is needed Including ASH, SQL Monitor etc. raises the question: What about licensing limitations for use of this function. As of current documentation there is no Enterprise Addition or additional management pack license needed for execution of DBMS_SQLDIAG.Report_SQL. The package DBMS_SQLDIAG and it's subroutines are often named as "SQL Repair Advisor". Looking at Features and Licensing there is no limitation for usage of SQL Repair Advisor and there's also a section for SQL Diagnostic Report confirming no limitation: The note "How To U...
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