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diff --git a/doc/virt_db.xml b/doc/virt_db.xml
index 9749f84..1fbdf96 100644
--- a/doc/virt_db.xml
+++ b/doc/virt_db.xml
@@ -19,13 +19,42 @@
DESCRIPTION
This filter allows one Z39.50 database to be me mapped to
- another target; or even multiple targets..
+ another target; or even multiple targets.
+
+
+ The configuration of virt_db consists of zero or more
+ <virtual> elements each describing the
+ Z39.50 virtual database recognized.
+ The name of the database is the text content of the
+ <database> element which should be
+ first element inside th virtual section.
+
+
+ Following that is one or more <target>
+ elements with the identifier of each target that the virtual database
+ maps to.
+
+
+ If multiple targets are given that has special meaning depending on the
+ filter following virt_db. If the following filter is load_balance, then
+ the load_balance filter will load balance between the targets given
+ (assuming they serve same content). If the following filter is multi,
+ then results will be merged from all targets instead.
+
+
+ The z3950_filter, on the other hand, does not support multiple targets.
+
+
+ For <virtual> a route may be given as
+ an attribute. This will make Metaproxy route traffic to the route
+ given. Note that virtual databases may not be combined if all
+ databases do not result in the same routing.
EXAMPLES
- A typical configuration looks like this:
+ Consider this virt_db configuration:
@@ -41,9 +70,22 @@
indexdata.com/gils
localhost:9999/Default
+
+ db3
+ indexdata.com/special
+
]]>
+ This will offer 4 databases, db1,
+ db2, combined and
+ db3. If a Z39.50 specifies db1
+ and db2 that will have same effect as specifying
+ the single database combined.
+
+
+ Since db3 routes differently from the other databases,
+ this database may not be combined with the others.
@@ -59,6 +101,10 @@
multi
3mp
+
+ load_balance
+ 3mp
+