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VDB Provisioned Datafiles for Temporary Tablespaces are only 50MB when Provisioning from Mounted Standby (KBA7998)

 

KBA

KBA# 7998

 

Issue

When provisioning from a mounted standby Oracle dSource, the VDB configuration will reflect the correct tablespaces and datafile names, but the size of each file may only be 50MB. The file size will not align with the expected configuration based on the Oracle source instance.

Prerequisites

This concern is only relevant for standby databases open in MOUNTED mode. Other standby database modes should not experience this behavior.

Applicable Delphix Versions

Click here to view the versions of the Delphix engine to which this article applies
Major Release All Sub Releases
6.0 6.0.0.0, 6.0.1.0, 6.0.1.1, 6.0.2.0, 6.0.2.1, 6.0.3.0, 6.0.3.1, 6.0.4.0, 6.0.4.1, 6.0.4.2, 6.0.5.0, 6.0.6.0, 6.0.6.1, 6.0.7.0, 6.0.8.0, 6.0.8.1, 6.0.9.0

5.3

5.3.0.0, 5.3.0.1, 5.3.0.2, 5.3.0.3, 5.3.1.0, 5.3.1.1, 5.3.1.2, 5.3.2.0, 5.3.3.0, 5.3.3.1, 5.3.4.0, 5.3.5.0, 5.3.6.0, 5.3.7.0, 5.3.7.1, 5.3.8.0, 5.3.8.1, 5.3.9.0

5.2

5.2.2.0, 5.2.2.1, 5.2.3.0, 5.2.4.0, 5.2.5.0, 5.2.5.1, 5.2.6.0, 5.2.6.1

5.1

5.1.0.0, 5.1.1.0, 5.1.2.0, 5.1.3.0, 5.1.4.0, 5.1.5.0, 5.1.5.1, 5.1.6.0, 5.1.7.0, 5.1.8.0, 5.1.8.1, 5.1.9.0, 5.1.10.0

5.0

5.0.1.0, 5.0.1.1, 5.0.2.0, 5.0.2.1, 5.0.2.2, 5.0.2.3, 5.0.3.0, 5.0.3.1, 5.0.4.0, 5.0.4.1, 5.0.5.0, 5.0.5.1, 5.0.5.2, 5.0.5.3, 5.0.5.4

Resolution

Ultimately, this datafile variance is expected, and is a result of Oracle standby database behaviors. 

Oracle will create the temporary tablespace datafiles tempfiles only if the standby has been opened read only and not in the mount state. In this condition, the datafiles will be present in v$tempfile but the size indicated will be 0 bytes. As a result, the controlfile details ingested as part of the Delphix SnapShot will reflect the same 0 byte size for these files. Any VDB provisioned from these snapshots will use the same detail for provision.

In the instance that any 0 byte temp file is present during VDB provisioning, a default file size of 52428800 bytes will be applied.

The following query can be used to confirm this condition on the standby instance linked as dSource:

select a.name,b.name, a.bytes from v$tempfile a, v$tablespace b where a.ts#=b.ts#;
select b.name, sum(a.bytes)/1024/1024/1024 from v$tempfile a, v$tablespace b where a.ts#=b.ts# group by b.name;

In the following example, we see two temporary tablespaces with 0 byte files indicated when querying the source.

SQL> select a.name,b.name, a.bytes from v$tempfile a, v$tablespace b where a.ts#=b.ts#;
NAME                               NAME                    BYTES
---------------------------------- ----------------------- ----------
+DATA01/DB1/TEMPFILE/temp1.1.dbf   TEMP1                   0
+DATA01/DB1/TEMPFILE/temp.2.dbf    TEMP                    0
SQL> select b.name, sum(a.bytes)/1024/1024/1024 from v$tempfile a, v$tablespace b where a.ts#=b.ts# group by b.name;
NAME                                               SUM(A.BYTES)/1024/1024/1024
-------------------------------------------------- ---------------------------
TEMP                                               0
TEMP1                                              0

As a result, the VDB provisioned from this dSource will create the temporary files with a default file size of 50MB (52428800 bytes).

 

If this behavior is undesirable, hook scripts can be leveraged to automatically extend the datafile(s) in question to align with the source or another other value, as desired. Delphix Documentation includes further detail on this product feature, if needed. Any additional assistance in creating hook scripts can be obtained from Delphix Professional Services:

https://docs.delphix.com/docs/datasets/getting-started/hook-scripts-for-automation-and-customization#HookScriptsforAutomationandCustomization-VirtualDatabaseHooks

 

 


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