Github user liuyu000 commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/995#discussion_r107580630
--- Diff: docs/cqd_reference/src/asciidoc/_chapters/query_execution.adoc ---
@@ -237,3 +237,54 @@ If you enable small scanner on large size scan
incorrectly, then you are likely
| *Deprecated In Release* | Not applicable.
|===
+<<<
+[[scratch-dirs]]
+== SCRATCH_DIRS
+
+[cols="25%h,75%"]
+|===
+| *Description* | Allows a CQD specification to override
the envvar settings for scatch and temporary file locations, which gives user
more flexibility to change scratch directory locations.
+| *Values* |
+Scratch disk locations for overflow (linux path names).
+
+Multiple locations can be specified, separated by a colon. For example,
/tmp/scratch1:/tmp/scratch2.
+
+| *Usage* a|
+
+*Two ways to change scratch directory location permanently*:
+
+* Specify this location at installation time.
+
++
+Currently the scratch directory locations are set at installation time.
The layer of scratch and temporary file system that manages the scratch file
creation and reads the envvar in $TRAF_HOME/etc/ms.env to determine where to
create the scratch files.
+
++
+The CQD will override envvar settings, there are two envvar settings: one
is STFS_HDD_LOACTION (default), the other is STFS_SSD_LOCATION (SSD disk).
+
++
+If the CQD is not set (empty), the envvar setting will work.
+
++
+The requirement is that the directories MUST exist on every node and
Trafodion user will need permission to write to those directories. If not, an
error will be returned when a query involving sort/hash overflow is executed.
--- End diff --
Got, thanks Dave. :)
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