Oracle: Explicitly Lock a Table

Hello all,
So I client had a process that kept need big chunks locks on a table. Problem is that due application use this lock occasionally failed (lock timeout) and the whole process fail. So how to guarantee this?

Using explicit locks for the table before starting the procedure, with command below:

LOCK TABLE GREPORA.GREP_TABLE IN SHARE MODE;

This lock is released as soon as the session commit or rollback transaction in the current session. Killing session means an implicit rollback, as usual.

The SHARE permits concurrent queries but prohibits updates to the locked table.

Nice right?
Hope it helps you too!

Adding new PDB to a CDB with Standby

On Oracle 12c we got a new feature on RMAN which allows you to restore database files, over the network, from a physical standby database by using the FROM SERVICE clause of the RESTORE command.

So in a Data Guard environment in case you add a new Pluggable database (PDB) you don’t need to duplicate the entire Container database (CDB) again. You can restore only the new PDB to the physical standby. Cool right, less work, faster work. I would prefer this as RMAN would do all its magic and we would not need to manual copies to renames.

On the practical side, this would be done in case you need to add a new PDB in your Data Guard configuration.

Stop the archive log apply on the standby using DG broker

validate database verbose PRIMARY;
validate database verbose STANDBY;
edit database 'STANDBY' set state='apply-off';
On the standby database restore the new PDB

rman target /
run{
allocate channel prim1 type disk;
set newname for pluggable database NEW_PDB to new;
restore pluggable database NEW_PDB from service PRIMARY;
switch datafile all;
}

– Enable recovery on the new PDB, if you running an Active DataGuard you need to stop it and start the standby database in mount, also if you get ORA-1113 make sure you are in MOUNT stage.

sqlplus / as sysdba
shtudown immediate
startup mount
alter session set container=NEW_PDB;
alter pluggable database enable recovery;
exit

– Enable archive log apply

edit database 'STANDBY' set state='apply-on';
validate database verbose PRIMARY;
validate database verbose STANDBY;

More information you can find on the MOS Note Making Use Deferred PDB Recovery and the STANDBYS=NONE Feature with Oracle Multitenant (Doc ID 1916648.1)

Hope it helps,
Elisson Almeida

OEM Report: Last 6 month Database Space Usage and Growth

Hello All!
So I had worked in some very useful reports to have in OEM. In next weeks I’ll share some code you may like… 🙂

To create it? Enterprise -> Reports -> Information Reports. There are several nice default reports there you me like.

Now, let’s go to the first Report, as per title:

1. First you Select the Database:

Select_DB.png

2. Then you see the report:

Report3

That’s nice, right?
Here is a report for another database with actual 640GB average growth per month (its expected, once DBSize is over 60TB):

Growth

So, Mat, can you share the queries? Of course:

Continue reading

Oracle Trigger Follows Clause: Simultaneous Ordered Triggers

Hi All!
I was reviewing some features in Oracle and, basically, every single time I review them I find something new. Seems Oracle Databases’ features are near to infinite and we frequently find some that can really add value to our solutions.

So here is something you may not be aware and is really cool:

Follows Clause

Oracle allows more than one trigger to be created for the same timing point, but up to version 11g is not possible to establish the execution order of execution. The Oracle 11g trigger syntax now includes the FOLLOWS clause to guarantee execution order for triggers defined with the same timing point.

The example below establish that second_trigger is executed after first_trigger before inserting each row in table_example.

CREATE OR REPLACE TRIGGER second_trigger
BEFORE INSERT ON table_example
FOR EACH ROW
FOLLOWS first_trigger
BEGIN NULL; END;
/

Nice, han?
Cheers!