- When Hot S tandby is active, this parameter determines how long the
+ When hot s tandby is active, this parameter determines how long the
standby server should wait before canceling standby queries that
conflict with about-to-be-applied WAL entries, as described in
.
- When Hot S tandby is active, this parameter determines how long the
+ When hot s tandby is active, this parameter determines how long the
standby server should wait before canceling standby queries that
conflict with about-to-be-applied WAL entries, as described in
.
Enables logging of recovery-related debugging output that otherwise
would not be logged. This parameter allows the user to override the
normal setting of , but only for
- specific messages. This is intended for use in debugging Hot S tandby.
+ specific messages. This is intended for use in debugging hot s tandby.
Valid values are DEBUG5 , DEBUG4 ,
DEBUG3 , DEBUG2 , DEBUG1 , and
LOG . The default, LOG , does not affect
rollforward will take considerably longer, so that technique only
offers a solution for disaster recovery, not high availability.
A standby server can also be used for read-only queries, in which case
- it is called a Hot Standby server. See for
- more information.
+ it is called a hot standby server. See
+ for more information.
- Hot S tandby feedback propagates upstream, whatever the cascaded arrangement.
+ Hot s tandby feedback propagates upstream, whatever the cascaded arrangement.
Hot Standby
- Hot S tandby is the term used to describe the ability to connect to
+ Hot s tandby is the term used to describe the ability to connect to
the server and run read-only queries while the server is in archive
recovery or standby mode. This
is useful both for replication purposes and for restoring a backup
to a desired state with great precision.
- The term Hot S tandby also refers to the ability of the server to move
+ The term hot s tandby also refers to the ability of the server to move
from recovery through to normal operation while users continue running
queries and/or keep their connections open.
being executed during recovery. This restriction applies even to
temporary tables, because table rows cannot be read or written without
assigning a transaction ID, which is currently not possible in a
- Hot S tandby environment.
+ hot s tandby environment.
In normal operation, read-only
transactions are allowed to
use LISTEN and NOTIFY ,
- so Hot S tandby sessions operate under slightly tighter
+ so hot s tandby sessions operate under slightly tighter
restrictions than ordinary read-only sessions. It is possible that some
of these restrictions might be loosened in a future release.
- There are also additional types of conflict that can occur with Hot S tandby.
+ There are also additional types of conflict that can occur with hot s tandby.
These conflicts are hard conflicts in the sense that queries
might need to be canceled and, in some cases, sessions disconnected to resolve them.
The user is provided with several ways to handle these
If hot_standby is on in postgresql.conf
(the default value) and there is a
standby.signal standby.signal for hot standby
- file present, the server will run in Hot S tandby mode.
- However, it may take some time for Hot S tandby connections to be allowed,
+ file present, the server will run in hot s tandby mode.
+ However, it may take some time for hot s tandby connections to be allowed,
because the server will not accept connections until it has completed
sufficient recovery to provide a consistent state against which queries
can run. During this period,
Caveats
- There are several limitations of Hot S tandby.
+ There are several limitations of hot s tandby.
These can and probably will be fixed in future releases:
Valid starting points for standby queries are generated at each
checkpoint on the primary. If the standby is shut down while the primary
- is in a shutdown state, it might not be possible to re-enter Hot S tandby
+ is in a shutdown state, it might not be possible to re-enter hot s tandby
until the primary is started up, so that it generates further starting
points in the WAL logs. This situation isn't a problem in the most
common situations where it might happen. Generally, if the primary is