Update of /home/cvsd/slony1/slony1-engine/doc/adminguide
In directory main.slony.info:/tmp/cvs-serv15587

Modified Files:
	faq.sgml 
Log Message:
Add to the FAQ a list of "impossible things" that people seem to keep asking for.


Index: faq.sgml
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  </qandaentry>
  
! <qandadiv>
  
  <qandadiv id="faqconnections"> <title> &slony1; FAQ: Connection Issues </title>
--- 367,432 ----
  </qandaentry>
  
! </qandadiv>
! 
! <qandadiv id="faqimpossibilities"> <title> &slony1; FAQ: Impossible Things People Try </title>
! 
! <qandaentry>
! <question><para> Can I use &slony1; to replicate changes back and forth on my database between my two offices? </para> </question>
! 
! <answer><para> At one level, it is <emphasis>theoretically
! possible</emphasis> to do something like that, if you design your
! application so that each office has its own distinct set of tables,
! and you then have some system for consolidating the data to give them
! some common view.  However, this requires a great deal of design work
! to create an application that performs this consolidation. </para>
! </answer>
! 
! <answer><para> In practice, the term for that is <quote>multimaster
! replication,</quote> and &slony1; does not support <quote>multimaster
! replication.</quote> </para> </answer>
! 
! </qandaentry>
! 
! <qandaentry>
! <question><para> I want to replicate all of the databases for a shared-database system I am managing.  There are multiple databases, being used by my customers.  </para> </question>
! 
! <answer><para> For this purpose, something like &postgres; PITR (Point
! In Time Recovery) is likely to be much more suitable.  &slony1;
! requires a slon process (and multiple connections) for each
! identifiable database, and if you have a &postgres; cluster hosting 50
! or 100 databases, this will require hundreds of database connections.
! Typically, in <quote>shared hosting</quote> situations, DML is being
! managed by customers, who can change anything they like whenever
! <emphasis>they</emphasis> want.  &slony1; does not work out well when
! not used in a disciplined manner.  </para> </answer>
! </qandaentry>
! 
! <qandaentry>
! <question><para> I want to be able to make DDL changes, and have them replicated automatically. </para> </question>
! 
! <answer><para> &slony1; requires that <xref linkend="ddlchanges"> be planned for explicitly and carefully.  &slony1; captures changes using triggers, and &postgres; does not provide a way to use triggers to capture DDL changes.</para>
! 
! <note><para> There has been quite a bit of discussion, off and on, about how
! &postgres; might capture DDL changes in a way that would make triggers
! useful; nothing concrete has emerged after several years of
! discussion. </para> </note> </answer>
! </qandaentry>
! 
! <qandaentry>
! <question><para> I want to split my cluster into disjoint partitions that are not aware of one another.  &slony1; keeps generating <xref linkend="listenpaths"> that link those partitions together. </para> </question>
! 
! <answer><para> The notion that all nodes are aware of one another is
! deeply imbedded in the design of &slony1;.  For instance, its handling
! of cleanup of obsolete data depends on being aware of whether any of
! the nodes are behind, and thus might still depend on older data.
! </para> </answer>
! </qandaentry>
! 
! <qandaentry>
! <question><para> I want to change some of my node numbers.  How do I <quote>rename</quote> a node to have a different node number? </para> </question>
! <answer><para> You don't.  The node number is used to coordinate inter-node communications, and changing the node ID number <quote>on the fly</quote> would make it essentially impossible to keep node configuration coordinated.   </para> </answer>
! </qandaentry>
! 
! </qandadiv>
  
  <qandadiv id="faqconnections"> <title> &slony1; FAQ: Connection Issues </title>