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Large file synchronisation

Efficiently synchronise copies of a large sparse file locally. I deal with a large amount of large sparse files because of virtualisation and other technologies. Because of their size, often a small number of blocks have data and, of these, a small number of blocks are changed and need to be backed up. Using a log-based (snapshotting) file system on USB 2 as a backup device, I only want to write blocks if absolutely necessary.

So what's the solution?  Some simple custom code that

  1. checks that both file sizes are identical;
  2. verifies that some metadata has changed (i.e time stamp, permissions or owner/group);
  3. reads both files block-by-block;
  4. writes only changed blocks to the destination file, and
  5. updates any changed metadata.
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Oracle Database 12c: Flex ASM enable an existing cluster

This HowTo demonstrates migrating a RAC cluster to Flex ASM from 'traditional' ASM.

The prerequisites are that the OCR files, ASM parameter file and ASM password file are stored in an ASM disk group with asm.compatible set to at least 12.1.  We will confirm the ASM cluster mode before we begin and after we have finished.

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Oracle Database 12c IPv6 enabled CRS RAC (Grid Infrastructure)

Oracle Database 12c Release 1 fully supports IPv6. Here is how to add IPv6 support to VIPs and SCANs in a 12c RAC cluster. The VIPs, SCANs and their listeners will support both IPv4 and IPv6 and addresses from both families will relocate between RAC nodes as normal. It is only assumed that the servers already have a host IPv6 address assigned via auto-configuration.

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Mapping UK crime data HowTo

QGIS showing Essex street crimes
Local street crimes in Basildon, Essex

We will create a database and populate it with UK streets and incidents of street crime. We will then plot the crimes on an interactive map for further analysis.

We will create a PostgreSQL PostGIS database on the local machine. Eventually all our spatial data will be stored here.

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Capacity trending graphs/charts in Oracle Grid Control

Example trending chart

Below I will annotate an example using SQL to extract and chart some tablespace trending data using GNU Plot.

Oracle's Grid Control collects, stores, and manages historical metric data for hosts, databases, and all sorts of targets. This data is difficult to retrieve, especially the historical data. Creating a report in Grid Control results in a small bitmapped image. If you need, say, a year of CPU data, this small bitmap is difficult to interpret.

If the data is extracted from Grid Control's Oracle Management Service (OMS) then graphically representing the data can also be performed externally. One such tool that can be used to graph the data is GNU Plot.

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Monitoring GoldenGate replicat performance using 'flashback query'

By using a checkpoint table in the OGG replicat database, you can retrospectively review the replicat's lag using flashback query (with some limitations if you do not utilise a heart beat table).

Picture the scenario. You receive observations that the Oracle GoldenGate (OGG) replicat system that you are responsible for had fallen behind overnight and all overnight processing was performed against incorrect data. What do you do? Perhaps the observation was erroneous. How can you demonstrate this?

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'ACID' compliant NoSQL document database

Following on from FoundationDB's graph store, they are now proposing a document store.  Again, there is emphasis on 'ACID' compliance.  So, unlike most other newcomers to the database scene, their database will support the protections familar to RDBMS database administrators.  The database should be protected from interference and corruption, and benefit from protection of saved transactions.

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