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Configuration Parameters (GUC)

Domino stream computing engine provides a comprehensive set of GUC parameters to finely control component behaviors.

Kernel GUC

Parameter	Description
`mx_stream_default_version`	Default version. Set to 2 to create v2 streams by default.
`mx_stream_internal_modify`	Used internally by stream computing. Controls whether data can be written into stream tables.
`mx_stream_debug_snapshot`	Whether to print debug information for historical snapshots.
`mx_stream_wal_keep_size`	Maximum XLog retention size for Domino v1/v2. Exceeding this value disables the stream (v1) or decoder (v2).
`mx_stream_enable_segment_set_launch`	Whether to start stream computing only on nodes within the segment_set.
`mx_enable_stream`	Global toggle for Domino v1.
`mx_stream_set_do_not_stream`	Prevents changes generated by REFRESH STREAM from participating in downstream stream computations.
`mx_max_number_streams`	Maximum number of streams allowed in Domino v1.
`mx_stream_worker_launch_timeout`	Time to wait before restarting a failed Domino v1 stream computing process; default is 1 minute.
`mx_stream_gc_period`	Interval for checking and handling leaked stream progress or slots in Domino v1; default is 5 minutes. Set to 0 to disable.
`mx_stream_base_backup_timeout`	Maximum time basebackup waits for stream computing to catch up to startptr; basebackup is aborted if this duration is exceeded.
`mx_stream_message_level`	Log level for Domino v1.

Domino v1 GUC

Parameter	Description
`mxstream.debug_tuple_decoding`	Controls whether v1 prints decoding debug information.
`mxstream.enable_sharescan`	Controls whether v1 enables sharescan.
`mxstream.debug_plan`	Controls whether execution plan EXPLAIN output is printed when creating a stream in v1.
`mxstream.debug_plan_costs` / `mxstream.debug_plan_verbose`	Controls what information is included in the EXPLAIN output when creating a stream in v1.
`mxstream.skip_decode`	Prevents writes in the current session from participating in stream computing; applies to both v1 and v2.
`mxstream.scan_xlog_size_limit`	Controls how much XLog is decoded per stream computation cycle in v1.
`mxstream.scan_tuples_limit`	Controls how many tuples are scanned per stream computation cycle in v1.
`mxstream.skip_valid_xlog`	Skips CRC checks for irrelevant records during v1 stream decoding.

Domino v2 GUC

Parameter	Description
`domino.debug` / `domino.debug2`	Enables or disables debug logging.
`domino.decode_interval`	Sets the decoding interval for the decoder. Only effective when decoding lag is below this value; otherwise, decoding proceeds as soon as possible.
`domino.enabled`	Global toggle for Domino v2. Controls whether the Domino ticker and scheduler processes are started. Default is off in version 6.3.X; requires restart to take effect.
`domino.max_number_decoders`	Maximum number of decoders in Domino v2. Each database uses one decoder; this limits the total number of supported databases.
`domino.max_workers`	Controls the number of Domino v2 worker processes. Workers are shared across databases that have stream tables.
`domino.max_streams`	Maximum number of streams in Domino v2; default is 1024. This parameter controls shared memory allocation and does not imply that creating 1024 streams is recommended.
`domino.job_retry_timeout_ms`	Time to wait before retrying after a stream execution failure; default is 60 seconds.
`domino.scan_limit`	Number of ticks to scan at once. Valid values: -1 means no limit; 1 means one tick at a time.
`domino.scan_interval`	Minimum interval between two consecutive scans in stream computing. Only takes effect when stream latency is less than decode_interval + scan_interval.
`domino.ticker_interval_mb` / `domino.ticker_interval_ms`	Interval for ticker to generate ticks, based on time elapsed or XLog growth.
`domino.tlog_keep_size (MB)`	Number of TLog files retained for stream computing. If stream processing falls behind decoding and exceeds this limit, TLog retention stops and the stream fails with error "could not open tlog file ...".
`domino.worker_timeout_ms`	Time after which the stream computing process automatically restarts.
`domino.streaming_leaf`	*Experimental feature* Controls whether output from the last-layer stream is decoded. Disabled by default. Can be enabled to alleviate performance bottlenecks. Not recommended to enable while creating streams, as enabling during upstream stream creation may cause missing data when downstream streams are added.

Function Practice