Goldengate Interview
Questions:
What type of Topology does
Oracle Goldengate support?
GoldenGate supports the following topologies.
More details can be foundhere.
- Unidirectional
- Bidirectional
- Peer-to-peer
- Broadcast
- Consolidation
- Cascasding
What are the main components of
the Oracle Goldengate replication?
The replication configuration consists of the
following processes.
- Manager
- Extract
- Pump
- Replicate
What database does Oracle
GoldenGate support for replication?
- Oracle
Database
- TimesTen
- MySQL
- IBM
DB2
- Microsoft
SQL Server
- Informix
- Teradata
- Sybase
- Enscribe
- SQL/MX
What transaction types does
Oracle 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?
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.
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 are macros?
Macro is an easier way to build your parameter
file. Once a macro is written it can be called from different parameter files.
Common parameters like username/password and other parameters can be included
in these macros. A macro can either be another parameter file or a library.
Where can macros be invoked?
The macros can be called from the following
parameter files.
- Manager
- Extract
- Replicat
- Gobals
How is a macro defined?
A macro statement consists of the following.
- Name
of the Macro
- Parameter
list
- Macro
body
Sample:
MACRO #macro_name
PARAMS (#param1, #param2, …)
BEGIN
< macro_body >
END;
MACRO #macro_name
PARAMS (#param1, #param2, …)
BEGIN
< macro_body >
END;
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 Oracle 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
What are the different
encryption levels in AES?
You can encrypt the password/data using the
AES in three different keys
a) 128 bit
b) 192 bit and
c) 256 bit
b) 192 bit and
c) 256 bit
Is there a way to check the
syntax of the commands in the parameter file without actually 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.
How can you increase the
maximum size of the read operation into the buffer that holds the results of
the reads from the transaction log?
If you are using the Classical Extract you may
use the TRANSLOGOPTION ASMBUFSIZE parameter to control the read size for ASM
Databases.
What information can you expect
when there us data in the discard file?
When data is discarded, the discard file can
contain:
1. Discard row details
2. Database Errors
3. Trail file number
1. Discard row details
2. Database Errors
3. 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
SEND EXTRACT ext_name, ROLLOVER
How can you determine if the
parameters for a process was recently changed
When ever a process is started, the parameters
in the .prm file for the process is written to the process REPORT. 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.
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.
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.
=================
OTHER :
Oracle DBA Goldengate interview questions:
OTHER :
Oracle DBA Goldengate interview questions:
1. What are the important process in GG?
2. What is difference between CSN, SCN?
3. What is extract, replicat?
4. What are the GG types or topologies?
5. How to get log from source & target?
6. Difference between classic & integral extract process?
7. What are the pre-request for GG?
8. Types of replication in GG?
9. What are the areas monitoring required in GG?
10. What is the difference between local trail / Remote Trail?
11. What are the GG utilities used?
12. How to define size for extract file?
13. How to change GG writing extract file?
14. How to purge extract file automatically?
15. How to check how many extract file created per day?
16. What to check, when replication steps in primary & target?
17. How to start/stop, extract/replicat for source & target?
18. How to sync target with source if we missed the trail file?
19. What is the format for trail file?
20. What is the default location for the trail file & can we change the trail file location?
21. What is the datapump in GG?
22. Is there any limit in extract groups / Replicat numbers?
23. What are the GG views?
24. What is GLOBAL file in GG & location?
25. What are the directory in GG?
26. What is credential store?
27. What are the types of encryption supported by GG?
28. What is obey usage?
29. What is discard file & usage? Can we change from default location?
30. How to switch writing to new trail file?
31. What is the proper steps to shutdown GG database?
32. How to automatically remove old trail file?
33. How to enable automatic for replicat/ extract?
34. What are the parameter file used by GG?
35. What are the limitation for bidirectional GG?
36. What is the use of REPERROR in GG?
37. How to check latency between source & GG?
38. What is utility used to open trail file in GG?
39. How to check particular trail file needed or not?
40. What are the various GG operational types?
41. What is reverse utility?
42. In unidirectional GG setup, steps to add a table for replication?
43. Can we change the GG oracle DB without setting up in operating system level?
44. What are the types extract check point positions?
45. How to change the trail file size in GG?
46. How to check all records processed in replicat? Info replicat group , it should return
47. How to calculate & allocate swap space for GG server?
48. How to check last 5 recent extract checkpoints?
49. How to control the checkpoint in extract & replicat?
50. How to confirm extract in working file in GG?
51. What are the recovery types in extract process?
52. How to setup lag process time in GG?
53. How to manager process to check extract/replicat lag?
54. How to view GG error log & process report?
55. How to check how many records processed in replication /extraction?
56. What is discard file? How to check default location?
57. How to check ,how many updates/deletes happened on GG in particular time?
58. what is archive log only mode in GG?
59. what is the command to see the recovery status in GG?
60.what is the use of SOURCEISTABLE &SPECIALRUN keyword in GG?
57. How to check ,how many updates/deletes happened on GG in particular time?
58. what is archive log only mode in GG?
59. what is the command to see the recovery status in GG?
60.what is the use of SOURCEISTABLE &SPECIALRUN keyword in GG?
==================================================================
How to Resync a Single Table with Minimum Impact to Other Tables' Replication? (Doc ID 966211.1)
============================================
1. When DDL is active, will be not able to perform Filtering,Mapping,Transformation of data.
2. Using GG - We can replicate DML and DDL Operations.
3. Can we move similar or dissimilar data across different Oracle Versions - YES.
4. GG Supports - Filtering,Mapping,Transformation of data.
5. Trail Files can reside on NAS / SAN
6. How do you estimate trail space.
To estimate required trail space
1. Estimate the longest time that the network could be unavailable. Plan to store enough
data to withstand the longest possible outage, because otherwise you will need to
resynchronize the source and target data if the outage outlasts disk capacity.
2. Estimate how much transaction log volume your business applications generate in one
hour.
3. Use the following formula to calculate the required disk space.
[log volume in one hour] x [number of hours downtime] x .4 = trail disk space
2. Using GG - We can replicate DML and DDL Operations.
3. Can we move similar or dissimilar data across different Oracle Versions - YES.
4. GG Supports - Filtering,Mapping,Transformation of data.
5. Trail Files can reside on NAS / SAN
6. How do you estimate trail space.
To estimate required trail space
1. Estimate the longest time that the network could be unavailable. Plan to store enough
data to withstand the longest possible outage, because otherwise you will need to
resynchronize the source and target data if the outage outlasts disk capacity.
2. Estimate how much transaction log volume your business applications generate in one
hour.
3. Use the following formula to calculate the required disk space.
[log volume in one hour] x [number of hours downtime] x .4 = trail disk space
============================================
FAQ: Most Common Goldengate Errors and Issues (Doc ID 1354649.1)
Oracle GoldenGate Logdump Complete Reference FAQ (Doc ID 1446672.1) ============================================
Oracle GoldenGate Logdump Complete Reference FAQ (Doc ID 1446672.1) ============================================
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