oracle goldengate interview questions

1) What are processes/components in GoldenGate?

Ans:

Manager, Extract, Replicat, Data Pump

2) What is Data Pump process in GoldenGate ?

he 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 can be seen as 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.


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


ANS: Golden Gate Command Line Interface essential commands – GGSCI

GGSCI   -- (Oracle) GoldenGate Software Command Interpreter


4) What is the default port for GoldenGate Manager process?

ANS:

7809

5) What are important files GoldenGate?

GLOBALS, ggserr.log, dirprm, etc ...


6) What is checkpoint table?

ANS:

Create the GoldenGate Checkpoint table

GoldenGate maintains its own Checkpoints which is a known position in the trail file from where the Replicat process will start processing after any kind of error or shutdown. 
This ensures data integrity and a record of these checkpoints is either maintained in files stored on disk or table in the database which is the preferred option.


7) How can you see GoldenGate errors?

ANS:

ggsci> VIEW GGSEVT
ggserr.log file

GoldenGate supports the following topologies. More details can be found here.

• Unidirectional
• Bidirectional
• Peer-to-peer
• Broadcast
• Consolidation
• Cascasding

What are the main components of the Goldengate replication?

The replication configuration consists of the following processes.

• Manager
• Extract
• Pump
• Replicate

What transaction types does Goldengate support for Replication?

Goldengate supports both DML and DDL Replication from the source to target.

What are the supplemental logging pre-requisites?

The following supplemental logging is required.

• Database supplemental logging
• Object level logging

Why is Supplemental logging required for Replication?

[sociallocker]When a 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.

List important considerations for bi-directional replication?

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

• Primary Key: Helps to identify conflicts and Resolve them.
• Sequences: Are not supported. The work around is 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.
• Packaged Application: These are not supported as it may contain data types which are not support by OGG or it might not allow the application modification to work with OGG.

Are OGG binaries supported on ASM Cluster File System (ACFS)?

Yes, you can install and configure OGG on ACFS.

Are OGG binaries supported on the Database File System (DBFS)? What files can be stored in DBFS?

No, OGG binaries are not supported on DBFS. You can however store parameter files, data files (trail files), and checkpoint files on DBFS.

What is the default location of the GLOBALS file?

A GLOBALS file is located under Oracle GoldenGate installation directory (OGG HOME)

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.
• Classic capture can’t read data from the compressed tables/tablespaces.

[/sociallocker]
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

I want to configure multiple extracts to write to the same exttrail file? Is this possible?

Only one Extract process can write to one exttrail at a time. So you can’t configure multiple extracts to write to the same exttrail.

What type of Encryption is supported in Goldengate?

Oracle Goldengate provides 3 types of Encryption.

• Data Encryption using Blow fish.
• Password Encryption.
• 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