Modifying Configuration Parameters of a DCS Instance

On the DCS console, you can configure parameters for an instance to achieve optimal DCS performance.

For example, to disable data persistence, set appendonly to no. For more instance parameters, see DCS Instance Configuration Parameters.

After the instance configuration parameters are modified, the modification takes effect immediately without the need to manually restart the instance. For a cluster instance, the modification takes effect on all shards.

Modifying Configuration Parameters of an Instance

Log in to the DCS console.
Click in the upper left corner of the management console and select the region where your instance is located.
In the navigation pane, choose Cache Manager.
On the Cache Manager page, click the name of the DCS instance you want to configure.
On the instance details page, choose Instance Configuration > Parameters.
Click Modify in the row containing the desired parameter. To modify multiple parameters at a time, click Modify above the parameter list.

Figure 1 Modifying parameter(s)
Modify parameters as required.

The parameters are described in DCS Instance Configuration Parameters. In most cases, you can retain default values.
After you have finished setting the parameters, click Save.
Click Yes to confirm the modification.

When the parameter modification task is in the Successful state, the parameter is modified.

DCS Instance Configuration Parameters

For more information about the parameters described in Table 1, visit https://redis.io/topics/memory-optimization.
Configurable parameters and their values vary depending on the instance type. If a parameter is not displayed in the Parameters page on the console, it cannot be modified.

**Table 1** DCS Redis instance configuration parameters
Parameter	Description	Exception Scenario	Value Range	Default Value
active-expire-num	Number of randomly checked keys in regular expired key deletions.	This parameter is not available for DCS Redis 3.0 and 6.0 professional edition instances.	1–1000	20
timeout	The maximum amount of time (in seconds) a connection between a client and the DCS instance can be allowed to remain idle before the connection is terminated. The value 0 indicates that the parameter is disabled. That is, the client is not disconnected when it is idle.	-	0–7200 Unit: second	0
appendfsync	Controls how often fsync() transfers cached data to the disk. Note that some OSs will perform a complete data transfer but some others only make a "best-effort" attempt.	Single-node instances do not have this parameter.	no: fsync() is never called. The OS will flush data when it is ready. This mode offers the highest performance. always: fsync() is called after every write to the AOF. This mode is very slow, but also very safe. everysec: fsync() is called once per second. This mode provides a compromise between safety and performance.	no
appendonly	Indicates whether to log each modification of the instance. By default, data is written to disks asynchronously in Redis. If this function is disabled, recently-generated data might be lost in the event of a power failure.	Single-node instances do not have this parameter.	yes: Logs are enabled, that is, persistence is enabled. no: Logs are disabled, that is, persistence is disabled. only-replica: Enable persistence only on replica nodes. NOTE: By default, the appendonly parameter can only be set to yes or no. To set it to only-replica for a basic edition master/standby or cluster DCS Redis 4.0/5.0/6.0 instance, or a professional (performance) edition master/standby one, contact O&M personnel.	yes
client-output-buffer-limit-slave-soft-seconds	When the client-output-buffer-slave-soft-limit parameter is exceeded for more than the value of this parameter, the server drops the connection.	-	0–60 Unit: second	60
client-output-buffer-slave-hard-limit	Hard limit on the output buffer of replica clients. Once the output buffer exceeds the hard limit, the client is immediately disconnected.	-	0–17,179,869,184 Unit: byte	1,717,986,918
client-output-buffer-slave-soft-limit	Soft limit on the output buffer of replica clients. Once the output buffer exceeds the soft limit and continuously remains above the limit for the time specified by the client-output-buffer-limit-slave-soft-seconds parameter, the client is disconnected.	-	0–17,179,869,184 Unit: byte	1,717,986,918
maxmemory-policy	The policy applied when the maxmemory limit is reached. 8 values are available.	-	volatile-lru: Evict keys by trying to remove the less recently used (LRU) keys first, but only among keys that have an expire set. allkeys-lru: Evict keys by trying to remove the LRU keys first. volatile-random: Evict keys randomly, but only among keys that have an expire set. allkeys-random: Evict keys randomly. volatile-ttl: Evict keys with an expire set, and try to evict keys with a shorter time to live (TTL) first. noeviction: Do not delete any keys and only return errors when the memory limit was reached. volatile-lfu: Evict keys by trying to remove the less frequently used (LFU) keys first, but only among keys that have an expire set. allkeys-lfu: Evict keys by trying to remove the LFU keys first. For details about eviction policies, see the Redis official website.	volatile-lru NOTE: If the DCS Redis instance is created before July 2020 and this parameter has not been modified, the default value is noeviction. If the instance is created after July 2020, the default value is volatile-lru.
lua-time-limit	Maximum time allowed for executing a Lua script.	-	100–5000 Unit: millisecond	5000
master-read-only	Sets the instance to be read-only. All write operations will fail.	Proxy Cluster instances do not have this parameter.	yes no	no
maxclients	The maximum number of clients allowed to be concurrently connected to a DCS instance. This parameter specifies the maximum number of connections on a single node (single shard). Cluster: Maximum connections per node = Maximum connections of the instance/Shard quantity Single-node and master/standby: Maximum connections on a single node = Maximum connections of the instance	Read/Write splitting instances do not support this parameter.	1000–50,000	10,000
proto-max-bulk-len	Maximum size of a single element request.	-	1,048,576–536,870,912 Unit: byte	536,870,912
repl-backlog-size	The replication backlog size. The backlog is a buffer that accumulates replica data when replicas are disconnected from the master. When a replica reconnects, a partial synchronization is performed to synchronize the data that was missed while replicas were disconnected.	-	16,384–1,073,741,824 Unit: byte	1,048,576
repl-backlog-ttl	The amount of time, in seconds, before the backlog buffer is released, starting from the last a replica was disconnected. The value 0 indicates that the backlog is never released.	-	0–604,800 Unit: second	3600
repl-timeout	Replication timeout.	Single-node instances do not have this parameter.	30–3600 Unit: second	60
hash-max-ziplist-entries	The maximum number of hashes that can be encoded using ziplist, a data structure optimized to reduce memory use.	-	1–10,000	512
hash-max-ziplist-value	The largest value allowed for a hash encoded using ziplist, a special data structure optimized for memory use.	-	1–10,000	64
set-max-intset-entries	When a set is composed entirely of strings and number of integer elements is less than this parameter value, the set is encoded using intset, a data structure optimized for memory use.	-	1–10,000	512
zset-max-ziplist-entries	The maximum number of sorted sets that can be encoded using ziplist, a data structure optimized to reduce memory use.	-	1–10,000	128
zset-max-ziplist-value	The largest value allowed for a sorted set encoded using ziplist, a special data structure optimized for memory use.	-	1–10,000	64
latency-monitor-threshold	The minimum amount of latency that will be logged as latency spikes If this parameter is set to 0, latency monitoring is disabled. If this parameter is set to a value greater than 0, all events blocking the server for a time greater than the configured value will be logged. To obtain statistics data, and configure and enable latency monitoring, run the LATENCY command. NOTE: The latency-monitor-threshold parameter is usually used for fault location. After locating faults based on the latency information collected, change the value of latency-monitor-threshold to 0 to avoid unnecessary latency.	Proxy Cluster instances do not have this parameter.	0–86,400,000 Unit: millisecond	0
notify-keyspace-events	Controls which keyspace events notifications are enabled for. If this parameter is configured, the Redis Pub/Sub feature will allow clients to receive an event notification when a Redis data set is modified. This parameter is disabled only when it is left blank.	Proxy Cluster instances do not have this parameter.	A combination of different values can be used to enable notifications for multiple event types. Possible values include: K: Keyspace events, published with the __keyspace@__ prefix E: Keyevent events, published with __keyevent@__ prefix g: Generic commands (non-type specific) such as DEL, EXPIRE, and RENAME $: String commands l: List commands s: Set commands h: Hash commands z: Sorted set commands x: Expired events (events generated every time a key expires) e: Evicted events (events generated when a key is evicted from maxmemory) A: an alias for "g$lshzxe" The parameter value must contain either K or E. A cannot be used together with any of the characters in "g$lshzxe". For example, the value Kl means that Redis will notify Pub/Sub clients about keyspace events and list commands. The value AKE means Redis will notify Pub/Sub clients about all events.	Ex
slowlog-log-slower-than	Slow queries cover scheduled commands whose execution is delayed. slowlog-log-slower-than is the maximum time allowed for command execution. If this threshold is exceeded, Redis will record the query.	-	0–1,000,000 Unit: microsecond	10,000
proxy-slowlog-log-slower-than	Slow queries of a proxy cover scheduled commands whose execution is delayed. proxy-slowlog-log-slower-than is the maximum time allowed for command execution. If this threshold is exceeded, the proxy will record the query.	Currently, only Proxy Cluster and read/write splitting instances in the CN East-Shanghai2 and CN South-Guangzhou regions.	30,000–2,000,000 Unit: microsecond	256,000
slowlog-max-len	The maximum allowed number of slow queries that can be logged. Slow query log consumes memory, but you can reclaim this memory by running the SLOWLOG RESET command.	-	0–1000	128
proxy-slowlog-max-len	The maximum allowed number of slow queries of a proxy that can be logged. Slow query log consumes memory, but you can reclaim this memory by running the SLOWLOG RESET command.	Currently, only Proxy Cluster and read/write splitting instances in the CN East-Shanghai2 and CN South-Guangzhou regions.	0–1000	128
auto-kill-timeout-lua-process	When this parameter is enabled, processes running the lua script are killed when their execution times out. However, scripts with write operations are not killed, but their nodes automatically restart (if persistence has been enabled for the instance) without saving the write operations.	Single-node instances and DCS Redis 3.0 instances do not have this parameter.	yes: enabled no: disabled	no
dispatch-pubsub-to-fixed-shard	This parameter specifies whether pub/sub channels are on the shard of slot 0. When this parameter is enabled, the pub/sub processing logic is consistent with that of single-node instances. You are advised to enable this parameter if you do not depend heavily on pub/sub. If you depend heavily on pub/sub, use the default configuration to allocate subscriptions to all shards.	Only Proxy Cluster instances have this parameter.	yes: Enable this parameter to allocate subscription channels to the shard of slot 0. no: Disable this parameter to allocate channels to the shard of each channel-hashed slot.	no
readonly-lua-route-to-slave-enabled	If enabled, read-only Lua scripts of read-only users are executed and routed to the standby node.	Only read/write splitting instances support this parameter.	yes: enabled no: disabled	no
cluster-sentinel-enabled	To support Sentinels for the instance.	Only Proxy Cluster instances have this parameter.	yes: enabled no: disabled	no
scan-support-wr-split	The SCAN command is executed on the master node when this parameter is disabled, or is executed on the standby node otherwise.	Only Proxy Cluster instances have this parameter. Proxy Cluster instances created earlier may not support this parameter. In this case, contact technical support to upgrade instances.	yes: enabled no: disabled	no

**Table 2** DCS Memcached instance configuration parameters
Parameter	Description	Value Range	Default Value
timeout	The maximum amount of time (in seconds) a connection between a client and the DCS instance can be allowed to remain idle before the connection is terminated. A setting of 0 means that this function is disabled.	0–7200 Unit: second	0
maxclients	The maximum number of clients allowed to be concurrently connected to a DCS instance.	1000–10,000	10,000
maxmemory-policy	The policy applied when the maxmemory limit is reached.	volatile-lru: Evict keys by trying to remove the less recently used (LRU) keys first, but only among keys that have an expire set. allkeys-lru: Evict keys by trying to remove the LRU keys first. volatile-random: Evict keys randomly, but only among keys that have an expire set. allkeys-random: Evict keys randomly. volatile-ttl: Evict keys with an expire set, and try to evict keys with a shorter time to live (TTL) first. noeviction: Do not delete any keys and only return errors when the memory limit was reached.	noeviction
reserved-memory-percent	Percentage of the maximum available memory reserved for background processes, such as data persistence and replication.	0–80	30