To answer my own question:
#
# Database drivers
#
# Given some of the available documentation, for example,
# http://aolserver.com/docs/admin/sample-db-config.tcl.txt
# you might expect Oracle configuration to follow the Sybase
# model and use an "external proxy daemon", but it does not.
#
# Also note the null {} datasource parameter.
#
ns_section "ns/db/drivers"
ns_param ora8 ora8.so ;# The ArsDigita Oracle driver
# Not needed for AD oracle driver.
#ns_section "ns/db/driver/ora8"
#ns_param localdaemon ??? ;# Name of the proxy daemon executable
ns_section "ns/db/pools"
ns_param main "Main Pool"
ns_param log "Log Pool"
ns_param subquery "Subquery Pool"
ns_section "ns/db/pool/main"
ns_param driver ora8
ns_param datasource {}
ns_param user foo
ns_param password bar
ns_param connections 5
ns_param logsqlerrors true ;# Verbose SQL query error logging
ns_param verbose false ;# Verbose error logging
ns_param maxidle 600 ;# Max time to keep idle db conn open
ns_param maxopen 3600 ;# Max time to keep active db conn open
ns_section "ns/db/pool/log"
ns_param driver ora8
ns_param datasource {}
ns_param user foo
ns_param password bar
ns_param connections 5
ns_param logsqlerrors true ;# Verbose SQL query error logging
ns_param verbose false ;# Verbose error logging
ns_param maxidle 600 ;# Max time to keep idle db conn open
ns_param maxopen 3600 ;# Max time to keep active db conn open
ns_section "ns/db/pool/subquery"
ns_param driver ora8
ns_param datasource {}
ns_param user foo
ns_param password bar
ns_param connections 2
ns_param logsqlerrors true ;# Verbose SQL query error logging
ns_param verbose false ;# Verbose error logging
ns_param maxidle 600 ;# Max time to keep idle db conn open
ns_param maxopen 3600 ;# Max time to keep active db conn open
#
# Accessing DB pools
#
# In the case of virtual servers you can give different virtual
# servers access to different databases, or you can let them access
# them all. AOLserver 3.x does not use virtual servers so the only
# useful value is "*", but if you use one config file for multiple nsd
# processes, or you are using a version of AOLserver that supports
# virtual servers, then you should list the pools you want to access.
#
ns_section "ns/server/${servername}/db"
ns_param pools * ;# Wildcard gives access to all
ns_param defaultpool main
An example of startup messages about a successful database configuration:
...
Notice: nsmain: AOLserver/3.4.2 starting
...
Notice: modload: loading '/opt/usr/local/aolserver/bin/ora8.so'
Notice: ora8 driver LobBufferSize = 16384
Notice: ora8 driver PrefetchRows = 0
Notice: ora8 driver PrefetchMemory = 0
Notice: Loaded ArsDigita Oracle Driver version 2.6, built on 22:04:36/Aug 26 2002