This post covers common questions related to Oracle GoldenGate 12c that we get frequently from our trainees from our training Oracle GoldenGate 12c Administration.
Common Questions on Oracle GoldenGate
Few questions on Oracle GoldenGate 12c raised by our trainees from our training Oracle GoldenGate 12c Administration:
Q1: What is the OGG s/w version to use if source DB is Oracle 12c R2 and platform Linux and destination is DB2 10.1 (32-bit) with 32-bit OS.
Does it mean we have to download and install separate OGG software versions at source and target servers? Will they be able to communicate with each other?
A1: In any case, you will have to install and configure Goldengate on both target and source even if versions are same. however, they will be two separate binaries.
Q2: Can the source platform be 32-bit and target platform on 64 bit OS for OGG implementation?
Q3: We ran an update statement in source database which updates ten million records, commit it and immediately run “shut abort” in the source database. Will data will get replicated correctly to the target database by OGG?
A3: If DB is down, Goldengate will abend. As long as data is written in logs when you restart the process goldengate will pick from the point where it stopped. So everything depends on what is getting written to logs and goldengate will pick committed transactions.
Q4: Instead of running ‘add trandata’, if I directly run ‘alter table add supplemental logging’ at SQL prompt, will OGG still work?
Q5: What happens if we add trandata for a table which do not have a primary key or unique key, but has invisible columns:
a) Will the invisible column will be considered for uniqueness while enabling supplemental logging?
b) What happens when we make the invisible column of the table visible?
A5: No invisible columns will not be considered for uniqueness if invisible columns are made visible they will be treated as normal columns.
Q6: When we talk about OGG initial load, the target tables should be empty, but the metadata should be present.
What about the indexes corresponding to the tables at the Target database?
Should they able be defined at the target database before starting OGG initial load?
A6: Goldengate Initial load takes care of only data. So yes metadata should be present. For faster load, it is advisable to turn off indexes but it’s not mandatory.
Q7: OGG “Skiptransaction” option can be provided only for replicat process? Can it be used for extract and data pump processes also?
A7: Replicat only
Q8: If both the source database and target database are RAC databases, will the OGG instances will also be RAC?
A8: There is no such thing called as OGG RAC. Only DB is RAC.
Q9: Under which circumstances do we need to run dblogin in ggsci?
Ans: Whenever any change to DB is required from GGSCI
Q10: If the file system on which trail files are stored gets filled up:
a) how will be the OGG processes behave? Will they get ABENDED?
Ans: Yes. OGG processes get ADENDED
b) How will the underlying source and databases behave?
Ans: Source and Target DB are independent of OGG hence no effect on DBS.
c) How will be the apply gap be detected and restored?
Ans: As soon as you restart the process, it will be taken care. This is done using Goldengate Checkpoint process.
If you wish to learn GoldenGate systematically then look at Activity Guides (tasks) you must perform from our Step by Step Guide to Learn Oracle GoldenGate or if you are already working/using Oracle GoldenGate then look at Oracle GoldenGate 12c Troubleshooting using Logdump Utility
This post is from our Oracle GoldenGate 12c Administration Training, in which we cover Architecture, Installation, Configuring & Preparing the Environment, DML Replication – Online Change Synchronization, Initial Load, Zero Downtime Migration & Upgrading using GoldenGate, Oracle GoldenGate Security, Performance of Oracle GoldenGate and Troubleshooting and much more.
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