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October 20, 2017

OGG (Oracle GoldenGate) Interview Questions

Oracle Golden Gate (OGG) Interview Questions/FAQs


1. What is GoldenGate and how to setup Golden Gate?


2. What are processes/components in OGG (Oracle Golden Gate)?

Manager, Extract, Replicat, Data Pump

3. What is (Data) Pump process in Golden Gate (OGG)?

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


5. What is the default port for Golden Gate Manager process?

7809

6. What are important files Oracle Golden Gate (OGG)?

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

7. What is checkpoint table?


8. How can you see Golden Gate errors?

ggsci> VIEW GGSEVT
ggserr.log file

9. What is the difference between classical extract and integrated extract?

Classic Capture/extract:
* 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)/Extract:
* In the Integrated Capture/Extract 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.


10. What is the difference between classical replicat and coordinated replicat?

11. How you will check whether replication is bidirectional (active-active setup) or not?

12. What is the use assumetargetdefs in replicat parameter file?
Use the ASSUMETARGETDEFS parameter when the source and target objects specified in a MAP statement have identical column structure, such as when synchronizing a hot site. It directs Oracle GoldenGate to assume that the data definitions of the source and target objects are identical, and to refer to the target definitions when metadata is needed for the source data.

13. Can you configure multiple extracts to write to the same exttrail file?
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.

14. What is the use passthru in pump parameter file?
parameter passthru indicate the source and target database tables structure are identical. In pass-through mode (configured by PASSTHRU), the Extract process does not look up table definitions from the database or from a data-definitions file. To use pass-through mode, the source and target table names and structures must be identical.

15. What is Handle collision in OGG?
The Goldengate HANDLECOLLISIONS parameter is configured on the target database in the Replicat process to enable processing of the data when there are duplicate data integrity issues in the destination database.
Use the HANDLECOLLISIONS and NOHANDLECOLLISIONS parameters to control whether or not Replicat tries to resolve duplicate-record and missing-record errors when applying SQL on the target.

16. List important considerations for bi-directional (active-active setup) 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.

17. What is the difference between Discard and Ignore (in RESOLVECONFLICT) ?


18. How you will check whether replicat is classical replicat or coordinated replicat or integrated replicat?

19. How to find out RBA of a Golden Gate (OGG) process ? [or] Which command will you use to find out the RBA of extract/replicat ?

20. What is heartbeat table in OGG ? Who will insert data into heartbeat table ?

21. How to check whether table is in OGG replication or not ?

Related Articles: Oracle DBA Interview Questions/FAQs – Part3   Oracle PL/SQL Interview Questions/FAQs   Oracle Performance related interview Questions/FAQs

1 comment:

  1. Merhaba,

    I’ve often thought about this Oracle GoldenGate Interview Questions/FAQs. Nice to have it laid out so clearly. Great eye opener.

    I'm trying to set up a reminder. It needs to remind users of a reassessment date that occurs every 90 days based upon the first contact (enrollment_date) with a potential client. But I only need to show the closest upcoming date. So, if a client's next closest assessment date is 12-12-15 it would show that date until 12-13-15 when it would be beginning to show 3-11-16. Is that possible?
    A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package. A cursor declared in a procedure is local to the procedure that cannot be accessed by other procedures.

    Appreciate your effort for making such useful blogs and helping the community.

    Obrigado,
    John

    ReplyDelete