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KBA1378 Block Change Tracking (BCT) and Delphix




This article is no longer current and is superseded by the documentation.




Q: Does Delphix recommend a file location or naming convention for block change tracking?

Generally speaking, the location and file name do not matter. However, there are exceptions to this:

  • If there are any known Oracle bugs related to block change tracking file locations and/or file names.
  • If running on an Oracle RAC, the block change tracking file should be in a shared location.

Q: When should I use BCT?

In general, Delphix recommends enabling Block Change Tracking (BCT) on a primary or standby source database. See Physical Standby Database Support Matrix in this topic for restrictions on enabling BCT on a standby database.

BCT is available from Oracle release onward for physical standby databases only if they are licensed for the Active Data Guard option.

  • Release is unstable for the BCT on physical standby feature
  • Release requires a patch for Oracle bug 7613481
  • Release requires patches for Oracle bugs 10170431, 12312133
  • Release requires patches for Oracle bugs 12312133, 16052165

Patches Required


Enabling BCT on a physical standby database without these patches is not recommended because of serious performance and stability issues.

If an Oracle installation has already been patched or once the patch is applied, use the CLI to update the repository for this installation so that appliedPatches includes the bug number(s) that has (have) been fixed. If the repository does not indicate that required bug(s) for the repository has (have) been addressed, SnapSync will show a warning about this(these) bug(s) for each SnapSync.

See Updating repository for Oracle applied patches with the Command Line Interface for details on how to update the repository.

BCT on a primary database has been stable since Oracle version

Q: What, if any, effects will BCT have on detaching a dSource?

 After reattaching the dSource Block Change Tracking will not be in sync, and the next SnapSync will need to read the entire database to determine which blocks have changed. 

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