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Delphix

Virtual Database Provisioning Performance May Degrade for Oracle 12c Databases (TB026)

Alert Type

Performance

Impact

The time taken to provision an Oracle Virtual Databases (VDBs) running Oracle 12c may be significantly longer in duration when compared with provision of the same data running an earlier version of Oracle.

Contributing Factors

The issue may occur in the following Delphix releases:

  • Delphix Engine 4.1.0.0 to 4.1.6.1
  • Delphix Engine 4.2.1.0 to 4.2.2.1

The issue can only occur if the source database is an Oracle 12c database with ASM and the target environment does not have ASM.

The issue may affect any Oracle 12c database, including those upgraded from prior Oracle releases.

The degradation in provisioning performance is directly proportional to the number of data files in an affected Oracle database.

Provision operations sourced from consistent Delphix Snapshots are not impacted. These include Snapshots where validated sync has already performed recovery and snapshots of standby Oracle databases where real-time apply is not active. 

Symptoms

The Oracle alert log of an affected VDB will contain one or more errors similar to the following:

Alert Log Messages
Starting background process ASMB
Sun Aug 16 01:38:25 2015
ASMB started with pid=23, OS id=906
WARNING: failed to start ASMB (connection failed) state=0x1 sid=''
WARNING: ASMB exiting with error

These errors will be repeated for each datafile in an affected Oracle database. 

Approximately 15 seconds is added to the provisioning time for each datafile in an affected VDB. For example, a VDB with 100 datafiles could take an additional 25 minutes to provision. 

Relief/Workaround

Provision to target environments where an ASM instance is running. 

As an alternative to starting ASM, Oracle Validated Sync for Oracle 12c, can be utilised to avoid long provision times, however this is only applicable for non multi-tenant databases. At the time of last update of this document (19.03.17) Delphix does not support validated sync for Oracle 12c multi-tenant databases.

Resolution

Resolution is available via Delphix Engine release 4.2.3.0 and later.

Additional Information

This issue occurs due to a change in the way Oracle handles certain database operations in Oracle 12c. For databases configured to use ASM, Oracle 12c attempts to start ASM-related services each time an affected operation is performed. Affected operations include listing or renaming datafiles.

The change with Oracle 12c is not specific to Delphix. However, because Delphix employs the affected operations, Oracle VDB provisioning is impacted.