Oracle12c_Snapshot_clone2_Ext
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ext4 filesystem utility
A small utility for ext4 filesystem will be presented
Dynamic sampling summary
In this post I'm going to summarize issues and strange behavior I've mentioned in my previous 2 posts: Oracle 11.2 Oracle 12.2 Empty stats Wrong stats Empty stats Wrong stats A single DYNAMIC_SAMPLING(10) hint Correct Wrong result Correct Wrong result A single DYNAMIC_SAMPLING_EST_CDN hint Almost correct Wrong result Almost correct Wrong result DYNAMIC_SAMPLING(10) and DYNAMIC_SAMPLING_EST_CDN … Continue reading Dynamic sampling summary
PDB Clone database serialization (18c case)
Here I continue to consider the mechnics for PDB "snapshot clone database" process serialization, today for 18c. In my test case I'm going again to create 10 PDB "simulteneously" and see what waits my sessions are suffer from. I will use a Tanel's Poder waitprof.sql script. A typical result would look like: % Total Total … Continue reading PDB Clone database serialization (18c case)
PDB Clone database serialization (12c case)
Here I am going to consider the mechnics for PDB Snapshot "clone database" process serialization, which prevents us from creating many PDBs simulteneously. (In ideal world you would like to create as much as you need PDBs for your unit tests on demand by several/many user sessions simulteneously but there are some limitations of this … Continue reading PDB Clone database serialization (12c case)
Dynamic sampling – empty stats case
My usecase: Create 2 tables: T_BIG usual heap table with correct all the time stats T_SMALL - "global temporary table" will have empty stats. /* Dynamic sampling issue clean stats */ spool 10c set lines 200 set pages 1000 DROP TABLE T_SMALL; DROP TABLE T_BIG; CREATE GLOBAL TEMPORARY TABLE T_SMALL ON COMMIT PRESERVE ROWS AS … Continue reading Dynamic sampling – empty stats case
Dynamic sampling- wrong stats case
My usecase: Create 2 tables: T_BIG will be untouched T_SMALL - "global temporary table" will contain much more records than stats claims. spool 10 set lines 200 set pages 1000 DROP TABLE T_SMALL; DROP TABLE T_BIG; CREATE GLOBAL TEMPORARY TABLE T_SMALL ON COMMIT PRESERVE ROWS AS SELECT rownum id, rpad('a',1000,'b') pad FROM dual connect by … Continue reading Dynamic sampling- wrong stats case
