Performance Tuning

How to Resolve "PMON failed to acquire latch, see PMON dump"

by Ed Chen
September 5, 2014April 20, 2018
2 Comments

PMON failed to acquire latch Here was the case, the database was hanging caused by some heavy loading processes. Users complained about the high waiting… Read More »

How to Resolve ORA-04031: unable to allocate 4216 bytes of shared memory

by Ed Chen
September 3, 2014December 11, 2022
2 Comments

Causes of ORA-04031 Found ORA-04031 in the alert log. ORA-04031: unable to allocate 4216 bytes of shared memory ("shared pool","unknown object","sga heap","library cache") Several kinds… Read More »

Timings to Set SESSIONS Explicitly

by Ed Chen
July 5, 2014May 17, 2019

DBAs usually set PROCESSES when initializing a new database:SQL> alter system set processes=3000 scope=both;System altered.Another important parameter SESSIONS will be derived from PROCESSES automatically in this… Read More »

How to Resolve ORA-01652: unable to extend temp segment by 8192 in tablespace

by Ed Chen
May 31, 2014May 12, 2023

ORA-01652 or ORA-1652 Permanent Tablespace SQL> INSERT INTO ERP35.PAY_HIST SELECT * FROM ERP35.PAY_TRANS; INSERT INTO ERP35.PAY_HIST SELECT * FROM ERP35.PAY_TRANS; * ERROR at line 1:… Read More »

ORA-29740 in Cluster Databases

by Ed Chen
March 6, 2013May 22, 2022

ORA-29740 ORA-29740 is an error message only for cluster databases, which indicates that an instance of the cluster is evicted by another member. It could… Read More »

ksbsrv: No Startup Acknowledgement From Forked Process After 30 Seconds

by Ed Chen
February 26, 2013March 28, 2018

If the database server was in performance bottlenecks, there could be various kinds of errors. Here is one case of low memory. First of all,… Read More »

How to Find out Badly Written Statements for Tuning

by Ed Chen
December 16, 2012October 10, 2021

When wait events like LIBRARY CACHE or LATCH FREE surges in business hours and the database seems to hang, you can check the free memory… Read More »

How to Monitor Real-Time Top SQL on CPU Consuming

by Ed Chen
December 6, 2012March 28, 2018

You can identify the most cpu-consuming SQL statements from database memory by querying v$sql.cpu_time, but they are not real-time data, they are history data. If… Read More »

How to Check Free Memory in SGA Pools

by Ed Chen
October 29, 2012March 28, 2018

The dynamic view gv$sga can tell you how much memory he occupied from OS. They won't change very often. The real available memory of SGA… Read More »

How to Check SGA Components Memory Distribution on Database 9i

by Ed Chen
October 28, 2012May 13, 2019

SGA Components For database 9i, there is no dynamic view gv$sgainfo like 10g or 11g that can represent current memory distribution of every component. Another… Read More »

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