[Oracle Target] When in Unlimited LOB mode, replication from SQL Database's NVARCHAR(MAX) type to Oracle's CLOB type fails with ORA-24806

[HNAKAGAW]

Hello support team

[Environment]

Source : Azure SQL Database

Target : Oracle 19c

[Situation]

- When in Unlimited LOB mode, replication from SQL Database's NVARCHAR(MAX) type to Oracle's CLOB type fails with ORA-24806.

- In both Full Load and Change Processing, when ORA-24806 occur , retries continue repeatedly.

- In Limited LOB mode, ORA-24806 does not occur in either FullLoad , Batch optimized apply , Transactional Apply.

- Changing the Oracle data type to NCLOB from CLOB prevents ORA-24806.

- Changing the Output Type of the column to CLOB in Table Settings > Transform does not prevent ORA-24806.

[Question]

Is there a workaround to prevent ORA-24806 from occurring while keeping Oracle data type CLOB?

Best Regards

Nakagawa

[Rahul_Kale]

Hello HNAKAGAW,

Thank you for reaching out to the Qlik community.
 

Yes, but there is no direct fix on the Oracle side while keeping CLOB. The workaround must ensure LOB character set/form consistency and avoid piecewise/LOB streaming mismatch.

To deal with this, you can try:-

• Align character set / LOB form (key fix)
  → Ensure client/buffer uses same charset as CLOB (not NCHAR).
• Use Limited / Inline LOB mode
  → Avoids piece‑by‑piece LOB streaming that triggers errors.
• Avoid implicit CLOB ↔ NCLOB conversions in mapping

[HNAKAGAW]

Hello Rahul_Kale

Thank you for your reply.

Regarding the second "Use Limited / Inline LOB mode", I understand where to find the relevant Qilk Replicate setting (Task Settings > Metadata > Target metadata > Limit LOB size to (KB)).

However, I’m not sure exactly what steps to take for the first "Align character set / LOB form (key fix)" and the third "Avoid implicit CLOB ↔ NCLOB conversions in mapping", so I would appreciate some clarification.

Best Regards

Nakagawa