Oracle Database

Oracle Database, read through Oracle REST Data Services: an instance that is not open, tablespaces filling up, sessions and processes against their limits, Data Guard lag, the fast recovery area and scheduler jobs that failed.

Network ports to open

From the DumbMonit server (or its relay agent) to the device:

Port	Protocol	Purpose
8080	TCP	ORDS (HTTP, default)
8443	TCP	Only if ORDS is served over TLS (HTTPS, default)

Why ORDS. Oracle’s native protocol (TNS) has no free implementation in pure Rust, and the usual drivers go through OCI, a proprietary C library (Instant Client) that cannot ship in DumbMonit’s static image and whose licence forbids redistributing it. ORDS is Oracle’s own free component that exposes the database over HTTP: with its REST-enabled SQL, a SELECT is posted as JSON to /ords/<schema>/_/sql, which is what DumbMonit does with the account’s own credentials. The limit is that ORDS must be deployed in front of the database. Where it is not, a script run by the DumbMonit agent (sqlplus) is the alternative; it is not provided here.

The account only holds CREATE SESSION and SELECT_CATALOG_ROLE: it reads the V$ and DBA_ views, and no data.

What it watches

All metrics are prefixed dumbmonit_oracle_.

Metric	What	Labels
version_info	value 1	version, status, database_status
instance_open	1 when the instance status is OPEN
uptime_seconds	since the instance started
database_info	value 1	open_mode, role, log_mode
tablespace_used_percent	use of each tablespace, against its maximum size	tablespace
sessions, sessions_used_percent	sessions, and their share of the sessions limit
processes, processes_used_percent	processes, and their share of the processes limit
dataguard_transport_lag_seconds, dataguard_apply_lag_seconds	Data Guard lag; only on a standby
recovery_area_used_percent	use of the fast recovery area; only when one is configured
scheduler_jobs_failed_24h	scheduler job runs that failed in the last 24 hours

Every query after the first is optional: a view the account cannot read leaves its metrics out without failing the check. A percentage is not written for a limit that is UNLIMITED.

The built-in rules that apply: Oracle instance not open, Oracle tablespace almost full, Oracle sessions near the limit, Oracle Data Guard apply lag, Oracle recovery area almost full, Oracle scheduler job failed, plus Monitor unreachable.

Let DumbMonit read Oracle through ORDS

1. Make sure Oracle REST Data Services (ORDS) runs in front of the database with REST-enabled SQL switched on.

   ords config set restEnabledSql.active true

2. As a privileged user, create the account DumbMonit will use, with the two rights it needs.

   CREATE USER dumbmonit IDENTIFIED BY "choose-a-long-password";
   GRANT CREATE SESSION, SELECT_CATALOG_ROLE TO dumbmonit;

3. Connected as that account, enable its schema for REST with the alias dumbmonit.

   EXEC ORDS.ENABLE_SCHEMA(p_enabled => TRUE, p_url_mapping_type => 'BASE_PATH', p_url_mapping_pattern => 'dumbmonit');

4. In DumbMonit, enter the ORDS address, for example ords.lan:8080 or https://ords.lan:8443, then the account and its password.

5. If the schema alias or the ORDS path differ from the defaults, set them in the options below.

Required permissions

• CREATE SESSION: Let the account log in
• SELECT_CATALOG_ROLE: Read the V$ and DBA_ views, no data

Warning

There is no native Oracle client: DumbMonit reads the database through ORDS over HTTP, and never contacts the listener on port 1521. The REST-enabled SQL settings vary between ORDS versions: check the ORDS documentation of yours.

Why these permissions

SELECT_CATALOG_ROLE gives read access to the data dictionary and performance views, never to application tables. REST-enabled SQL authenticates with the database account, so the account’s schema has to be enabled for REST; the alias in the URL is the schema alias (dumbmonit by default, the account name in lower case).

Credentials

Credential	Fields
Username / password	The database account created above, sent as HTTP basic authentication to ORDS.

Address: the ORDS host (ords.lan), host:port, or a full URL. Options: protocol (HTTP by default), port (8080), ORDS path (/ords), schema alias (empty: the account name in lower case), certificate check, request timeout (10 s).