CATEGORY / Oracle GoldenGate

Oracle GoldenGate Parallel Internals – my presentation from POUG 2018

Oracle GoldenGate Parallel Integrated Replicat – DML rearrangement in transactions

While preparing my presentation for POUG 2018 conference I have found some different behavior in Parallel Intgrated Replicat. This is a new Replicat type available from version 12.3. According to Oracle internal tests Parallel Replicat can be up to 5 times faster than Integrated Replicat in the same test case. I have done a number of tests with various options but one thing struck me. Every time the Replicat rearranges the order of DML operations. And there is no way to turn it off.

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Oracle GoldenGate data filtering with WHERE and FILTER parameters the right way

One of the most trivial tasks for data replication is to define a replica of the table with just a subset of the rows from the source table. For example we would like just to replicate the ACCOUNTS table with some type (one column has some defined value). If you want to replicate that using Oracle GoldenGate and the account type may be modified then this is one of the most difficult tasks to achieve… Let’s find out why.

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Oracle GoldenGate point in time source database recovery

Even though you would like to secure the database from any disaster with HA, still it might happen that the database gets corrupted and a recovery from backup is needed to recover the database. In a critical scenario you might need to use Point In Time Recovery (PITR).

Let’s focus on a scenario when the source database needs to be recovered from backup to an earlier point in time. How to resync a replication to the target  database  without the need of a  full initial load?

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Oracle GoldenGate Coordinated Replicat unsynchronized mode troubleshooting

According to the Oracle GoldenGate Coordinated Replicat documentation if the Replicat is stopped in an unclean manner the threads may be unsynchronized. Different threads may reach different checkpoint positions.

Let’s find out what what might be the consequences of this situation.

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Oracle GoldenGate Coordinated Replicat – is it a fully transactional replication?

Oracle GoldenGate till version 11.2 could only work serially. The only way of creating parallel replication and speeding up the apply process was to create multiple Replicat processes. In version 12.1 there was a new option available: the Coordinated Replicat. It is often misunderstood as a way of speeding up transactional replication. But … is this way of replication fully ACID complaint? Let’s find out. (more…)

Oracle GoldenGate Replicat Checkpoint table

In one of my previous posts I have described the rationale for using a checkpoint table in the Replicat process. This is a summary of all possible combinations of Replicat process and which of them are able of (not) using checkpoint table.

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Oracle GoldenGate Integrated Replicat and NOSCHEDULINGCOLS

According to the documentation it is not allowed to use NOSCHEDULINGCOLS with ADD TRANDATA when you would use Integrated Replicat. Why would Oracle care for that? Let’s find out what can happen if you don’t apply the rules.

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Oracle GoldenGate Classic Replicat checkpointing

One of the key aspects for replication is checkpointing. A target database checkpoint tells which transactions are actually committed and which not yet. This is a key aspect of transactional replication. Let’s look how that works for the Oracle GoldenGate Classic Replicat.

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Oracle GoldenGate remote Classic Extract

Most people I have spoken to are are absolutely convinced that the Extract process has to be running on the source database host. This thinking comes from all Oracle diagrams where the Extract process is located on the source database host. Till OGG version 11.1.1 this was indeed true. Some have heard that the Extract process can be removed from the source host but it can only done with the Integrated Extract process.

There is however the TRANLOGOPTIONS DBLOGREADER parameter which allows the Classic Extract can be run remotely without any need of accessing the redo/archive logs file system (or ASM).

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