Oracle GoldenGate Interview Questions

 

1) What type of Topology does Goldengate support?

GoldenGate supports the following topologies.

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

2) What are the main components of the Goldengate replication?

The replication configuration consists of the following processes.

  • Manager
  • Extract
  • Pump
  • Replicate

3) What transaction types does Goldengate support for Replication?

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

4) What are the supplemental logging pre-requisites?

The following supplemental logging is required.

  1. Database supplemental logging
  2. Object-level logging

5) Why is Supplemental logging required for Replication?

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.
  • This Capture mode supports extracting data from source databases using compression.
  • Integrated Capture can be configured in an online or downstream mode.

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

The following are the minimum required parameters that must be defined in the extract parameter file.

  • EXTRACT NAME
  • USERID
  • EXTTRAIL
  • TABLE

7) I want to configure multiple extracts to write to the same extra file? Is this possible?

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

8) What type of Encryption is supported in Goldengate?

Oracle Goldengate provides 3 types of Encryption.

  • Data Encryption using Blowfish.
  • Password Encryption.
  • Network Encryption.

9) What are the different password encryption options available with OGG?

You can encrypt a password in OGG using

  • Blowfish algorithm and
  • Advanced Encryption Standard (AES) algorithm

10) What are the different encryption levels in AES?

You can encrypt the password/data using the AES in three different keys

  1. 128 bit
  2. 192 bit
  3. 256 bit

  4. 11) What are some of the key features of GoldenGate 12c?

    The following are some of the more interesting features of

    • Support for Multitenant Database
    • Coordinated Replicat
    • Integrated Replicat Mode
    • Use of Credential store
    • Use of Wallet and master key
    • Trigger-less DDL replication
    • Automatically adjusts threads when RAC node failure/start
    • Supports RAC PDML Distributed transaction
    • RMAN Support for mined archive logs

    12) What are the installation options available in OGG 12c?

    You can install Oracle GoldenGate 12c using in 2 ways:

    • Interactive Installation with OUI – Graphical interface
    • Silent Installation with OUI – Command Interface

    13) What is a Credential Store in OGG 12c?

    OGG Credential Store manages Encrypted Passwords and USERIDs that are used to interact with the local database and Associate them with an Alias.

    Instead of specifying actual USERID and Password in a command or a parameter file, you can use an alias. The Credential Store is implemented as an auto-login wallet within the Oracle Credential Store Framework (CSF). know more at Oracle golden gate online training

    14) How to configure the Credential Store in OGG 12c?

    Steps to configure Oracle Credential Store are as follows:

    Step 1:

    By Default Credential Store is located under “dircrd” directory.
    If you want to specify a different location use can specify the “CREDENTIALSTORELOCATION” parameter in the GLOBALS file.
    Example: CREDENTIALSTORELOCATION /u01/app/oracle/OGG_PASSWD

    Step 2:

    • Goto OGG home and connect to GGSCI.
    • cd $OGG_HOME
    • /ggsci
    • GGSCI>

    15) What command is used to create the credential store?

    ADD CREDENTIAL STORE

    16) How do you add credentials to the credential store?

    • ALTER CREDENTIALSTORE ADD USER userid,
    • [PASSWORD password]
    • [ALIAS alias]
    • [DOMAIN domain]

    Example: GGSCI> ALTER CREDENTIALSTORE ADD USER GGS@orcl, PASSWORD oracle ALIAS extorcl DOMAIN OracleGoldenGate

    17) How do you retrieve information from the Oracle Credential Store?

    GGSCI> INFO CREDENTIALSTORE
    OR
    GGSCI> INFO CREDENTIALSTORE DOMAIN OracleGoldenGate

    18) What are the different data encryption methods available in OGG 12c?

    In OGG 12c you can encrypt data with the following 2 methods:

    • Encrypt Data with Master Key and Wallet
    • Encrypt Data with ENCKEYS

    19) How do you enable Oracle GoldenGate for Oracle database 11.2.0.4?

    The database services required to support Oracle GoldenGate capture and apply must be enabled explicitly for an Oracle 11.2.0.4 database.

    This is required for all modes of Extract and Replicat.

    To enable Oracle GoldenGate, set the following database initialization parameter. All instances in Oracle RAC must have the same setting.

    • ENABLE_GOLDENGATE_REPLICATION=true

    20) How does the Replicat works in a Coordinated Model?

    In a Coordinated Mode Replicat operates as follows:

    • Reads the Oracle GoldenGate trail.
    • Performs data filtering, mapping, and conversion.
    • Constructs SQL statements that represent source database DML or DDL transactions (in committed order).
    • Applies the SQL to the target through the SQL interface that is supported for the given target database, such as ODBC or the native database interface.

    • 21) What is the difference between Classic and Coordinated Replicat?

      The difference between classic mode and coordinated mode is that Replicat is multi-threaded in coordinated mode. know more at Oracle golden gate training

      Within a single Replicat instance, multiple threads read the trail independently and apply transactions in parallel. Each thread handles all of the filtering, mapping, conversion, SQL construction, and error handling for its assigned workload.

      A coordinator thread coordinates the transactions across threads to account for dependencies among the threads.

      22) How do you create a COORDINATED REPLICATE in OGG 12c?

      You can create the COORDINATED REPLICATE with the following OGG Command:

      • ADD REPLICATE rfin, COORDINATED MAXTHREADS 50, EXTTRAIL dirt/et

      23) I have created a Replicat process in OGG 12c and forgot to specify the DISCARDFILE parameter. What will happen?

      Starting with OGG 12c, if you don’t specify a DISCARDFILE OGG process now generates a dicard file with default values whenever a process is started with START command through GGSCI.

      24) Is it possible to start OGG EXTRACT at a specific CSN?

      Yes, Starting with OGG 12c you can now start Extract at a specific CSN in the transaction log or trail.
      Example:

      • START EXTRACT fin ATCSN 12345
      • START EXTRACT finance AFTERCSN 67890

      25) List a few parameters which may help improve the replicate performance?

      The parameters below can be used to improve the replicate performance:

      • BATCHSQL
      • GROUPTRANSOPS
      • INSERTAPPEND

      Oracle Goldengate Interview Questions For Experienced

      26) What are the areas to monitor in Goldengate Replication?

      The lag and checkpoint latency of the Extract, pump and Replicat processes are normally monitored.

      27) What is the PASSTHRU mode used for?

      In pass-through mode, the Extract process does not look up the table definitions, either from the database or from a data definitions file.

      This increases the throughput of the data pump, as the object definition lookup is bypassed.

      28) What are the most common reasons for an Extract process slowing down?

      Some of the possible reasons are:

      • Long-running batch transactions on a table.
      • Insufficient memory on the Extract side. Uncommitted, long-running transactions can cause the writing of a transaction to a temporary area (dirtmp) on a disk. Once the transaction is committed it is read from the temporary location on the file system and converted to trail files.
      • Slow or overburdened Network.

      29) What are the most common reasons for the Replicat process slowing down?

      Some of the possible reasons are:

      • A large number of transactions on a particular table.
      • Blocking sessions on the destination database where non-Goldengate transactions are also taking place on the same table as the replicate processing.
      • If using DBFS, writing & reading of trail files may be slow if SGA parameters are not tuned.
      • For slow Replicat’s, latency may be due to missing indexes on target.
      • Replicat having to process Update, delete of rows in very large tables.

      30) My extract was running fine for a long time. All of a sudden it went down. I started the extract processes after 1 hour. What will happen to my committed transactions that occurred in the database during the last 1 hour?

      OGG checkpoint provides the fault tolerance and makes sure that the transaction marked for committed is capture and captured only once. know more at Oracle golden gate online course

      Even if the extract went down abnormally, when you start the process again it reads the checkpoint file to provide the read consistency and transaction recovery.

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