</indexterm>

<listitem>

<para>

Specifies the maximum number of concurrent connections from standby

servers or streaming base backup clients (i.e., the maximum number of

simultaneously running WAL sender

processes). The default is zero. This parameter can only be set at

server start. <varname>wal_level</> must be set to <literal>archive</>

or <literal>hot_standby</> to allow connections from standby servers.

Specifies the maximum number of concurrent connections from

standby servers or streaming base backup clients (i.e., the

maximum number of simultaneously running WAL sender

processes). The default is zero, meaning replication is

disabled. WAL sender processes count towards the total number

of connections, so the parameter cannot be set higher than

<xref linkend="guc-max-connections">. This parameter can only

be set at server start. <varname>wal_level</> must be set

to <literal>archive</> or <literal>hot_standby</> to allow

connections from standby servers.

</para>

</listitem>

</varlistentry>

if (ReservedBackends >=MaxBackends)

if (ReservedBackends >=MaxConnections)

{

write_stderr("%s: superuser_reserved_connections must be less than max_connections\n",progname);

ExitPostmaster(1);

}

if (max_wal_senders >=MaxConnections)

{

write_stderr("%s: max_wal_senders must be less than max_connections\n",progname);

ExitPostmaster(1);

}

if (XLogArchiveMode&&wal_level==WAL_LEVEL_MINIMAL)

ereport(ERROR,

(errmsg("WAL archival (archive_mode=on) requires wal_level \"archive\" or \"hot_standby\"")));