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Performance Problems From Running LOB Functions In The “insert Into “ Statement (Doc ID 2437537.1)

Last updated on SEPTEMBER 28, 2018

Applies to:

Oracle Database - Enterprise Edition - Version 12.1.0.2 and later
Information in this document applies to any platform.

Symptoms

Source table '<table 1>' has smaller data columns ( byte ) .

Intermediate table '<table 2> has columns VARCHAR2(4000 CHAR)'

Final Table '<table 3> has columns VARCHAR2(4000 CHAR)'

Inserting table1 with Byte =====> table2  with VARCHAR2 column is fast with 100+ seconds only

Inserting table2 with VARCHAR2 column =====> table3 with VARCHAR2 column takes 3000+ seconds

Byte to CHAR insert is fast rather than reading from CHAR to and inserting into CHAR.

In short:

VARCHAR2(4000 byte) datatype table to VARCHAR2(4000 CHAR) datatype table INSERT is working fine with 100+ seconds

VARCHAR2(4000 CHAR) datatype table to VARCHAR2(4000 CHAR) datatype table INSERT is taking long as 3000+ seconds




Changes

This is with MAX_STRING_SIZE=EXTENDED in 12c.

Cause

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