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:


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!

Optimize fragmented tables in MySQL

It happens on MySQL, as you know. Run an Optimize Table solve the question.
BUT, be careful! During the optimize the table stay locked (writing is not possible).

(Fragmented Table)

So what?
To not cause a lock in every table, the script below shows and runs (if you want to list but not run, comment the line) only for tables that have fragmentation.

It was very useful to me! 🙂

echo -n "MySQL username: " ; read username
echo -n "MySQL password: " ; stty -echo ; read password ; stty echo ; echo
mysql -u $username -p"$password" -NBe "SHOW DATABASES;" | grep -v 'lost+found' | while read database ; do
mysql -u $username -p"$password" -NBe "SHOW TABLE STATUS;" $database | while read name engine version rowformat rows avgrowlength datalength maxdatalength indexlength datafree autoincrement createtime updatetime checktime collation checksum createoptions comment ; do
if [ "$datafree" -gt 0 ] ; then
fragmentation=$(($datafree * 100 / $datalength))
echo "$database.$name is $fragmentation% fragmented."
mysql -u "$username" -p"$password" -NBe "OPTIMIZE TABLE $name;" "$database"

The resul will be like:

MySQL username: root
MySQL password:
mysql.db is 12% fragmented.
mysql.db optimize status OK
mysql.user is 9% fragmented.
mysql.db optimize status OK

This script is a full copy from this post by Robert de Bock.
Thanks, Robert!


Rebuild all indexes of a Partioned Table

Another quick post!

Regarding you frequently need to collect all indexes of a partioned table (local and global indexes), this is a quick script that make the task a little bit easier:

-- local indexes
for i in (select p.index_owner owner, p.index_name, p.partition_name
from dba_indexes i, dba_ind_partitions p
where i.owner='&OWNER'
and   i.table_name='&TABLE'
and   i.partitioned='YES'
and   i.visibility='VISIBLE' -- Rebuild only of the visible indexes, to get real effect :)
and   p.index_name=i.index_name
and   p.index_owner=i.owner
order by 1,2) loop
execute immediate 'alter index '||i.owner||'.'||i.index_name||' rebuild  partition '||i.partition_name||' online parallel 12'; -- parallel 12 solve most of the problems
execute immediate 'alter index '||i.owner||'.'||i.index_name||' parallel 1'; -- If you don't use parallel indexes in your database, or the default parallel of the index, or what you want...
end loop;
-- global indexes
for i in (select i.owner owner, i.index_name
from dba_indexes i
where i.owner='&OWNER'
and   i.table_name='&TABLE'
and   i.partitioned='NO'
and   i.visibility='VISIBLE' -- same comment
order by 1,2) loop
execute immediate 'alter index '||i.owner||'.'||i.index_name||' rebuild online parallel 12'; -- same
execute immediate 'alter index '||i.owner||'.'||i.index_name||' parallel 1'; -- same :)
end loop;

I hope this script make your life easier. Hugs!