Oracle Goldengate Interview Q and A

 Oracle Goldengate Interview Q and A

GOLDENGATE QUESTIONS AND ANSWERS

What type of Topology does goldengate support?

GoldenGate supports the following topologies.

-Unidirectional

-Bidirectional

-Peer-to-peer

-Broadcast

-Consolidation

-Cascading

What are the main components of the Goldengate replication?

The replication configuration consists of the following processes.

-Manager

-Extract

-Pump

-Replicat

What database does GoldenGate support for replication?

- oracle database

-TimesTen

- mysql

-IBM DB2

-Microsoft SQL Server

-Informix

- teradata

-Sybase

-Enscribe

-SQL/MX

-NOSQL

-INFORMIX

What transaction types does Goldengate support for Replication?

Goldengate supports both dml nd DDL Replication from the source to target.

DDL and DML could be enabled separately without enabling the other transaction types.

What are the Goldengate setup pre-requisites?

Source:

The following supplemental logging is required. -

Database supplemental logging

Object level supplemental logging (ADD TRANDATA)

Database level Goldengate user with Goldengate level privileges for extraction of data from source database.

Target:

Database level Goldengate user with Goldengate level privileges for replication of data to target database.

Why is Supplemental logging required for Replication?

When a transaction transaction is committed on the source database, only new data is written to the Redo log. However for oracle to apply these transactions on the destination database, the before image key values are required to identify the effected rows. This data is also placed in the trail file and used to identify the rows on the destination, using the key value the transactions are executed against them.

So to say in few words, to uniquely identify the row Supplemental logging is required.

Why are the Parameter files in Goldengate?

Parameter files are heartbeat of Goldengate. Goldengate process works based on Parameters defined in Parameter files. Every Process in Goldengate has its own Parameter file.

What is the location of Report files?

The report file for each process is written inside dirrpt. Goldengate stored 10 latest report file for each process in dirrpt.

Which Parameter id used to housekeep the trail Files of Goldengate?

PURGEOLDEXTRACTS is used in manager parameter file to housekeep the trail files.

I want to view description regarding a particular Parameter. Is there any parameter in Goldengate?

From 12.2 onwards u can use parameter INFO PARAM <PARAMETER NAME> in GGSCI.

GGSCI> info param <PARAMETER NAME>

List important considerations for bi-directional replication?

Bi-directional Replication is of two types:

Active-Active

Active-Passive

The customer should consider the following points in an active-active replication environment.

Primary Key: Helps to identify conflicts and Resolve them.

Sequences: You can use to use odd/even, range or concatenate sequences.

triggers: These should be disabled or suppressed to avoid using uniqueness issue

Data Looping: This can easy avoided using OGG itself

LAG: This should be minimized. If a customer says that there will not be any LAG due to network or huge load, then we don’t need to deploy CRDs. But this is not the case always as there would be some LAG and these can cause Conflicts.

CDR (Conflict Detection & Resolution): OGG has built in CDRs for all kind of DMLs that can be used to detect and resolve them.

What is data pump process in Goldengate?

The Data Pump (not to be confused with the Oracle Export Import Data Pump) is an optional secondary Extract group that is created on the source system. When Data Pump is not used, the Extract process writes to a remote trail that is located on the target system using TCP/IP. When Data Pump is configured, the Extract process writes to a local trail and from here Data Pump will read the trail and write the data over the network to the remote trail located on the target system.

The advantages of this be it protects against a network failure as in the absence of a storage device on the local system, the Extract process writes data into memory before the same is sent over the network. Any failures in the network could then cause the extract process to abort (abend). Also, if we are doing any complex data transformation or filtering, the same can be performed by the Data Pump. It will also be useful when we are consolidating data from several sources into one central target where data pump on each individual source system can write to one common trail file on the target.

Where can filtering of data for a column be configured?

Filtering of the columns of a table can be set at the Extract, Pump or Replicat level.

Is it a requirement to configure a PUMP extract process in OGG replication?

A PUMP extract is an option, but it is highly recommended to use this to safe guard against network failures. Normally it is configured when you are setting up OGG replication across the network.

What are the differences between the Classic and integrated Capture?

Classic Capture:

The Classic Capture mode is the traditional Extract process that accesses the database redo logs (optionally archive logs) to capture the DML changes occurring on the objects specified in the parameter files.

At the OS level, the GoldenGate user must be a part of the same database group which owns the database redo logs.

This capture mode is available for other rdbms as well.

There are some data types that are not supported in Classic Capture mode.

There are some restrictions on Classic Capture which cant be captured by Classic Capture.

Integrated Capture (IC):

In the Integrated Capture mode, GoldenGate works directly with the database log mining server to receive the data changes in the form of logical change records (LCRs).

IC mode does not require any special setup for the databases using ASM, transparent data encryption, or Oracle RAC.

This feature is only available for oracle databases in Version 11.2.0.3 or higher.

 It also supports various object types which were previously not supported by Classic Capture.

This Capture mode supports extracting data from source databases using compression.

Integrated Capture can be configured in an online or downstream mode.

List the minimum parameters that can be used to create the extract process?

The following are the minimium required parameters which must be defined in the extract parameter file.

EXTRACT NAME

USERID

EXTTRAIL

TABLE

What is the command line utility in GoldenGate (or) what is ggsci?

Golden Gate Command Line Interface essential commands – GGSCI

GGSCI   — (Oracle) GoldenGate Software Command Interpreter

What type of Encryption is supported in Goldengate?

Oracle Goldengate provides 3 types of Encryption.

Data Encryption using Blow fish.

Password Encryption in dircrd

Network Encryption.

What are the different password encrytion options available with OGG?

You can encrypt a password in OGG using

Blowfish algorithm and

Advance Encryption Standard (AES) algorithm

Is there a way to check the syntax of the commands in the parameter file without running the GoldenGate process?

Yes, you can place the SHOWSYNTAX parameter in the parameter file and try starting. If there is any error, you will see it.

What information can you expect when there us data in the discard file?

When data is discarded, the discard file can contain:

Discard row details

Database Errors

Trail file number

What command can be used to switch writing the trail data to a new trail file?

You can use the following command to write the trail data to a new trail file. SEND EXTRACT ext_name, ROLLOVER

How can you determine if the parameters for a process was recently changed?

Whenever a process is started, the parameters in the. prm file for the process is written to the process . You can look at the older process reports to view the parameters which were used to start up the process. By comparing the older and the current reports you can identify the changes in the parameters.