Wednesday Apr 16, 2014

How fast can I replicate data?

Oracle GoldenGate is a very powerful instrument for logical data replication and this post's title is intentionally silly. Why silly? Read this and find out. The contents, instead, is very serious.

You won't need to master it, but there's some math you must be aware of in order not to fool yourself in a logical replication scenario.

[Read More]

Friday Apr 11, 2014

Exadata hard disk usage at hand

On board each Exadata Storage Server there's an Exadata specific version of OS Watcher. It's a gold mine of information, with a very thin level of detail.

I had to study the effect of write back flash cache: the following awk script extracts %util of the most used hard disk from iostat archives of OS Watcher.

Enjoy!

BEGIN {
          timeStamp="0";
}
/^sd[a-z] / {
          extractedField=$12;
          if ( a[timeStamp] < extractedField ) {
              a[timeStamp] = extractedField;
          }
}

/^zzz/ {
          sampleDate=sprintf("%s/%s/%s", $7, $3, $4);
}

/^Time/ {
          timeStamp=sprintf("%s %s", sampleDate, substr($2,1,5));
}
END {
          for ( ia in a ) {
                  printf ("\"%s\",\"%s\"\n", ia, a[ia]);
          }
}

Here is a sample graph you can generate with the data obtained in such way.

% Uitl of most used disk

NOTE: Exadata documentation is not public. I'd love to explain where OS Watcher is on cells and many other details... but, if you are interested in this topic, you have Exadata and you can access plenty of documentation!

NOTE2: The simple script discussed here extracts information about the most used physical disk, which is not representative of the overall cell operation. It just derives from a very specific interest of mine. Fell free to adapt it to your needs.



Saturday Mar 15, 2014

sql*plus command history on Linux

RLWRAP is your friend

A customer of mine has complained about the inability to easily grab a previously submitted command in sql*plus.

Refrain from migrating the platform you are on, and use rlwrap.

  1. install the OS package "rlwrap" available in your linux distro
  2. define the following bash function in your .bash_profile
sp () {
  rlwrap sqlplus ${@:-/nolog}
}


Enjoy using sp instead of sqlplus!

Wednesday Mar 12, 2014

Alert summary, a simple and improvable tool

A simple awk script to summarize the content of your database's alert.log.[Read More]

Friday Mar 07, 2014

Ten questions to answer when thinking of logical data replication

Logical database replication may be an eagerly required "toy" in your organization. The success of new reporting applications, (near) real time data distribution and processing and so forth may heavily depend on it - and take it for granted.

This isn't surprising at all: data is supposed to appear and steadily kept current. Vendors, including Oracle, claim they are able to provide very efficient, near real time and even heterogeneous instruments to achieve this result.

With such a variety of replication solutions you have plenty of time to evaluate how strong is your concept of logical replication (and its implications), how your organization is ready to maintain it and make sure nobody will point a finger at you when it breaks.

Have a look at the following 10 simple questions and have some additional fun before playing with technology!

[Read More]
About

Enrico Brambilla is an Oracle Core Technology Expert, member of Oracle Consulting. He has worked with over a hundered big and small customers across the years, gathering thoughts to share about Database, e-BS, Exadata, GoldenGate and more - not "just" technology.

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