Pro's and Con's of default variable $_ in Perl

In this post we will see some good practice while you write your Perl scripts . If you see my previous post Getting started with Awesome Perl I have discussed usage of default variable $_ while what we see in this post how good for a programmer is to use the default variable

It's for sure that the default variable ($_) does the work but when you have a large chunk of code , readability of the code will become a problem . Lets take a piece of code and analyze it .

Let's pass some sql data into an array like one shown below

my @data = `db2 "list tables for schema DB2INST1"`

Now the array @data is populated with some data , lets go and do some manipulations

Accidents happen - Recovering a dropped table

A must quality of a DBA is to know the recovery strategy first before entering the battlefield .That is the reason I have started the Accidents happen series so that we can discuss further recovery strategies in this series of posts.

I have not found many search results where somebody who could show in detail how to recover an accidentally dropped table . So I thought of giving an example scenario as it will help at least some people who are dealing with it for the first time.

The first precaution you can take is to add WITH RESTRICT ON DROP clause to the CREATE TABLE

Say you created a table as shown below

CREATE TABLE "DB2INST1"."EMPLOYEE" ( "EMPNO" CHAR(6 OCTETS) NOT NULL , "FIRSTNME" VARCHAR(12 OCTETS) NOT NULL , "MIDINIT" CHAR(1 OCTETS) , "LASTNAME" VARCHAR(15 OCTETS) NOT NULL , "WORKDEPT" CHAR(3 OCTETS) , "PHONENO" CHAR(4 OCTETS) , "HIREDATE" DATE , "JOB" CHAR(8 OCTETS) , "EDLEVEL" SMALLINT NOT NULL , "SEX" CHAR(1 OCTETS) , "BIRTHDATE" DATE , "SALARY" DECIMAL(9,2) , "BONUS" DECIMAL(9,2) , "COMM" DECIMAL(9,2) )  
IN "USERSPACE1"     
WITH RESTRICT ON DROP       
ORGANIZE BY ROW  ;

Getting started with Awesome Perl

Perl : Practical Extraction and Report Language is one of the widely used scripting language . I will be discussing this post in the DBA perspective . Most of our Databases reside on either Linux or Windows servers , so we choose either Shell or Batch scripting .

Lets take a case you been very comfortable writing shell script's as your databases resides on Linux box's ,but for some reason your client decided to move or migrate them to windows machines where there's a definite necessity for you to port all your shell scripts to batch script , you know you need to start all the way from bottom .

So who helps us from this kind of situations , Perl , yes one big advantage of Perl is it portability . Make sure you have the Perl compiler installed either in your Linux or Windows machine and you are free from platform concerns .

Let's see some basics of Perl and some sample scripts

Shell

Perl

public - beware of this pseudo group

It was almost 3 years back when my career started , I had a chance of creating users and granting them privileges where i created a user and was shocked the moment i created a user in OS he could connect to the database even before granting privileges to him.

This eventually led me to the documentation where i came to know the pseudo group rather PUBLIC group is the culprit.Culprit ? No No ... Not actually , DB2 may have launched this to make things a bit easier for DBA , granting some predefined set of privileges to the user created .

But if you don't believe in accidents and don't want to leave any loopholes , then you may not be very comfortable with this group as it leaves some control over to others

Now lets get into work , db2 has provided us with various tables under SYSCAT catalog schema for administrating authorizations and privileges , here is one way you can look them

Storage groups - A comprehensive solution of handling your data

Monday, 20 January 2014 Storage groups manohar viswanatha

Presumptions :

In this post we assume 3 mount points namely C:\ , D:\ , E:\ .

C:\ & D:\ are considered to be SSD's and

E:\ is considered to be a RAID device or normal HDD

I have gone through Ember's recent post A Few Differences When Moving From 9.7 to 10.1 where I came across storage groups - a new way of handling physical data .I just thought of giving it a try and went through the db2 v10.1 documentation where the feature was introduced , let me tell you db2 is getting rock-steady version by version

Don't be an ORTHODOX DBA

Most of the times we DBA's take on the developers like underdogs , even I used to but things have changed as my years of experience in the industry is growing by , Every person is equally important right from the application developers, DB developers, Network Administrator.... to DBA's . Anyone one role in the Software life Cycle is neglected , the whole application gets affected

I myself have neglected DB Development like creating procedures . Recently , very recently I happened to create some custom stored procedures which will help the DBA's , they save a lot of time

Ill discuss one case I have come across , I usually use the google drive to store my documents where in I store all my custom administrative queries I use daily

I use to copy paste the respective query depending on my need , because all the time you don't have sufficient time to write the query every time , say a tablespace DMS container size is full for some reason and you need to EXTEND it immediately , You cannot frame the query at that peak time which will be time consuming as every second counts

One day there came a issue and I don't have my laptop on hand , so connected through my other colleagues system where in I cannot access my google drive as I'm already connected to VPN , by the time I framed the query and issued the command some transactions in the application got affected

I then started thinking after resolving this issue as to how can I save this time I have wasted in framing my query at that peak time which made to go through basics of STORED PROCEDURES and yes they really help me a lot

Friendship between REORG and Temp Tablespace's - Part2

In my previous post we have discussed about REORG utility and some monitoring utilities for REORG

Friendship between REORG and Temp Tablespace's

Normally when you issue a REORG on a table like one below

REORG TABLE DB2INST1.EMPLOYEE

db2 does the reorganization of the table in the same tablespace it is residing on ,which is not a good thing always , especially when your data is growing there is no sense in doing reorg in the same tablespace and disturbing the other physical objects like tables and MQT's performance

That is where system temporary tablespaces save us from the performance degradations while REORG

So how do we achieve this ? , we create separate bufferpools for all different page sizes i.e., 4K, 8K, 16K, 32K

Friendship between REORG and Temp Tablespace's

Let us look into what db2 does when a traditional classic offline REORG on a table is issued

When you issue the REORG TABLE DB2INST1.EMPLOYEE the table EMPLOYEE will go through the following phases shown in the image

Let's go through what actually is happening in these phases