apache/cassandra · error · InvalidRequestException

Cannot enable accord on system tables

Error message

Cannot enable accord on system tables (%s.%s)

What it means

Transactional Mode (Accord) cannot be enabled on tables in the system keyspaces. validateAndUpdateTransactionalMigration (AlterTableStatement.java:642) rejects any altered TableParams whose transactionalMode has Accord enabled when SchemaConstants.isSystemKeyspace(keyspaceName) is true, since internal tables must keep the default transactional behavior.

Solutions

1. Do not enable Accord on system tables; keep transactional_mode = 'off' for them
2. Apply the transactional_mode change to your application keyspaces' tables only
3. If a generated script targets system tables, exclude them from the migration

Example fix

// before
ALTER TABLE system.local WITH transactional_mode = 'accord';
// after
ALTER TABLE my_app.orders WITH transactional_mode = 'accord';

if (SchemaConstants.isSystemKeyspace(ks) && params.transactionalMode.accordIsEnabled) { /* skip or reject the alteration before sending */ }

try { session.execute(alterStmt); } catch (InvalidRequestException e) { if (e.getMessage().startsWith("Cannot enable accord on system tables")) { /* exclude system keyspaces from migration */ } else throw e; }

When it happens

Trigger: ALTER TABLE system.some_table WITH transactional_mode = 'accord' (or any Accord-enabled mode), applied via CQL or a programmatic TableParams alteration on a keyspace like system, system_schema, etc.

Common situations: Trying to experiment with Accord-based transactions on internal tables; schema generation tools copying table params from an application keyspace onto a system table.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Counters are not supported with Accord for table
• Cannot change transactional mode from
• Cannot change transactional mode to
• Cannot enable accord on system tables
• ACCESS TO DATACENTERS operations not supported by…

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/b89405fa46f27f52. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/cql3/statements/schema/AlterTableStatement.java:642

        @Override
        public void validate(ClientState state)
        {
            super.validate(state);
            // If a memtable configuration is specified, validate it against config
            if (attrs.hasOption(TableParams.Option.MEMTABLE))
                MemtableParams.get(attrs.getString(TableParams.Option.MEMTABLE.toString()));
            Guardrails.tableProperties.guard(attrs.updatedProperties(), attrs::removeProperty, state);

            TableParams paramsForValidation = attrs.asNewTableParams(keyspaceName);
            validateDefaultTimeToLive(paramsForValidation);
            validateMinimumTrainingFrequencyForDictionaryCompressor(paramsForValidation);
        }

        private TableParams validateAndUpdateTransactionalMigration(boolean isCounter, TableParams prev, TableParams next)
        {
            if (next.transactionalMode.accordIsEnabled && SchemaConstants.isSystemKeyspace(keyspaceName))
                throw ire("Cannot enable accord on system tables (%s.%s)", keyspaceName, tableName);

            boolean modeChange = prev.transactionalMode != next.transactionalMode;
            boolean wasMigrating = prev.transactionalMigrationFrom.isMigrating();
            boolean explicitlySetMigrationFrom = attrs.hasOption(Option.TRANSACTIONAL_MIGRATION_FROM);
            // set table to migrating
            TransactionalMigrationFromMode newMigrateFrom = TransactionalMigrationFromMode.fromMode(prev.transactionalMode, next.transactionalMode);

            if (isCounter && (next.transactionalMode != TransactionalMode.off || newMigrateFrom != TransactionalMigrationFromMode.none || next.transactionalMigrationFrom != TransactionalMigrationFromMode.none))
                throw ire(format(ACCORD_COUNTER_TABLES_UNSUPPORTED, keyspaceName, tableName));

            boolean forceMigrationChange = modeChange && explicitlySetMigrationFrom && next.transactionalMigrationFrom != newMigrateFrom;

            if (modeChange && next.transactionalMode.accordIsEnabled && !DatabaseDescriptor.getAccordTransactionsEnabled())
                throw ire(format("Cannot change transactional mode to %s for %s.%s with accord.enabled set to false",
                                 next.transactionalMode, keyspaceName, tableName));

            // user is manually updating migration mode, don't interfere
            if (forceMigrationChange)

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