Oracle Database as our consultants live it every day: installation and patching, upgrades, RMAN backup and recovery, Data Guard, RAC, performance tuning, multitenant, licensing, and engineered systems such as ODA and Exadata.
By Franck Pachot . I like that Oracle drops the datafiles from the operating system when we remove them from the database (with drop tablespace or drop pluggable database) because I don’t like to have orphean files remaining in the filesystem. However, to ensure that space is reclaimed, we must be sure that Oracle did not leave a process with…
By Franck Pachot . More and more we can see crazy queries generated by ORM frameworks or BI query generators. They are build to be easily generated rather than being optimal. Then, the optimizer has to implement more and more transformations to get an efficient execution plan. Here is one new that appeared in Oracle 12cR2: Subquery Elimination when the…
In this post we are going to deploy a R.A.C system ready to run production load with near-zero knowledge with R.A.C, Oracle cluster nor Oracle database. We are going to use the “Deploy Cluster Tool” which is provide by Oracle to perform Oracle deployment of many kind of database architectures you may need like Oracle single instance, Oracle Restart or…
By Franck Pachot . Did you notice that each time you want to download the Oracle binaries from the OTN website (for non-production usage) you have to click on the “Accept License Agreement”? This is because you have to agree with the OTN license agreement, and that makes it not easy to distribute an automated way to build an environment.…
In Oracle 12.2 an archive log directory is accepted, if top level directory does not exist: oracle@localhost:/u01/app/oracle/product/12.2.0/dbhome_1/dbs/ [DMK] ls -l /u02/oradata/DMK/ total 2267920 drwxr-xr-x. 2 oracle dba 96 Dec 6 05:36 arch … Now database accepts this non existing archivelog destination: SQL> alter system set log_archive_dest_3=’LOCATION=/u02/oradata/DMK/arch/arch2′; System altered. But not this: SQL> alter system set log_archive_dest_4=’LOCATION=/u02/oradata/DMK/arch/arch2/arch4′; alter system set log_archive_dest_4=’LOCATION=/u02/oradata/DMK/arch/arch2/arch4’…
If you store your databases on the cluster filesystem ACFS you may use the provided Perl-script gDBClone from OTN to clone databases or create snapshot databases. It is an interesting approach to create clones from the Production DB in minutes regardless of the production DB size. What you do is to create a standby DB from your production DB on…
By Franck Pachot . A quick post to show why you should always use LOGTIME=ALL METRICS=Y when using Data Pump. Just look at an example showing the timestamp in front of each line and a message about each task completed by the worker: 15-NOV-17 11:48:32.305: W-5 Processing object type DATABASE_EXPORT/SCHEMA/PROCACT_SCHEMA 15-NOV-17 11:48:34.439: W-13 Completed 28 PROCACT_SCHEMA objects in 1 seconds…
By Franck Pachot . When I explain the multitenant internals, I show that all metadata about system procedures and packages are stored only in CDB$ROOT and are accessed from the PDBs through metadata links. I take an example with DBMS_SYSTEM that has nothing in SOURCE$ of the PDB. But I show that we can compile it from the PDB. This…
By Franck Pachot . The title of this blog post was: “Tracing DBMS_RCVMAN for reclaimable archivelogs” until I started to write the conclusion… In a previous post I mentioned that there’s a bug with archivelog deletion policy when you want to mention both the ‘BACKED UP … TIMES TO …’ and ‘APPLIED’ or ‘SHIPPED’ as conditions for archived logs to…
By Franck Pachot . There are several bugs with the optimizer in FIRST_ROWS mode. Here is one I encountered during a 10.2.0.4 to 12.2.0.1 migration when a view had an ‘order by’ in its definition. Here is the test case that reproduces the problem. A big table: SQL> create table DEMO1 (n constraint DEMO1_N primary key,x,y) as select 1/rownum,’x’,’y’ from…
By Franck Pachot . On datawarehouse databases, I frequently recommend increasing the level of dynamic sampling because: Queries have complex predicates with AND, OR, IN(), ranges and correlated values for which the optimizer cannot estimate the cardinality properly Queries are long anyway (compared to OLTP) and can afford more parse time to get an optimized execution plan However, there’s a…
After having worked with OVM on various architectures I can say that it is a good technology to easily build virtualized environments for production applications. Because it is based on XEN and has simple ways to deal with existing storage (FC, ISCSI, NFS, …) and networking solution (bond, lacp, …) it is a robust and convenient way to virtualized IT…
