High 'SQL*Net message from client' when querying LOB tables (Doc ID 1590389.1)

Last updated on FEBRUARY 24, 2017

Applies to:

Oracle Net Services - Version 10.2.0.1 to 12.1.0.1 [Release 10.2 to 12.1]
Information in this document applies to any platform.

Symptoms

Statements that involve tables with LOB data (CLOB or BLOB column) and that SELECT the LOB column are very slow and will take some time to finish. This is especially noticeable if the client is remote or on a WAN.
Increasing the SDU and/or increasing the number of fetched rows (in sqlplus 'set arraysize') will not make any difference.

Trace level 10046 and/or AWR reports will show the following SQL*NET wait events:
      SQL*Net message from client
      SQL*Net message from dblink
as top events in term of number of occurances ("Times Waited") and total time spent ("Total Waited").

Cause

Sign In with your My Oracle Support account

Don't have a My Oracle Support account? Click to get started

My Oracle Support provides customers with access to over a
Million Knowledge Articles and hundreds of Community platforms