diff --git a/gpdb-doc/dita/install_guide/migrate.xml b/gpdb-doc/dita/install_guide/migrate.xml
index 5a34780d23e026d34b0c4ff7a1926d7e4893b63e..77d7309ecdb97015db7536f422ab06b301ce3580 100644
--- a/gpdb-doc/dita/install_guide/migrate.xml
+++ b/gpdb-doc/dita/install_guide/migrate.xml
@@ -137,6 +137,11 @@
aggregate in a previous Greenplum release that called the built-in
int4_avg_accum() function, you will need to revise your aggregate for
the new signature.
+
The string_agg(expression) function has been removed from Greenplum 6.
+ The function concatenates text values into a string. You can replace the single argument
+ function with the function string_agg(expression, delimiter) and specify
+ an empty string as the delimiter, for example
+ string_agg(txt_col1, '').
gpbackup saves the distribution policy and distribution key for each
table in the backup so that data can be restored to the same segment. If a table's
distribution key in the Greenplum 4.3 or 5 database is incompatible with Greenplum 6,