When multiple jobs compete for shared level-2 subscription quota resources, the scheduling policy determines which job gets resources first. MaxCompute supports two policies: first-in-first-out (FIFO) scheduling, where jobs queue up behind each other so the earliest-submitted job runs first; and fair scheduling, which distributes resources across all running jobs simultaneously. Choosing the right policy determines how computing resources are allocated among concurrent jobs in a quota group.
Usage notes
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Job priority scheduling takes precedence over the quota scheduling policy. Resources are allocated to higher-priority jobs first. When jobs share the same priority, the configured scheduling policy applies.
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Scheduling policies cannot be configured for level-2 quotas of the Interactive type.
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From May 24, 2023, FIFO scheduling is the default policy for level-2 quotas of new projects in all regions. Projects created before May 24, 2023 use fair scheduling by default. For details, see Service notices.
Compare scheduling policies
| Fair scheduling | FIFO scheduling | |
|---|---|---|
| How resources are allocated | Distributed evenly across all jobs submitted at the same time. Higher-priority jobs get an even share first; remaining resources go to lower-priority jobs. | Allocated in full to the earliest-submitted job. Higher-priority jobs take precedence regardless of submission order. |
| Best for | Teams where multiple engineers submit jobs simultaneously and each job needs to start promptly. Also suitable when multiple baselines share a quota group and must all run at the same time — otherwise, the output of the baseline job is affected. | Batch pipelines where all submitted jobs are treated as a single workload and total throughput matters more than the start time of any individual job. |
| Advantage | Multiple jobs can run at the same time. | The average operation time of a single job is short. |
| Risk | Individual jobs take longer because resources are shared across concurrent workloads. | A large job can occupy most resources, causing other jobs in the same quota group to queue indefinitely. |
Mitigating FIFO queue buildup
If jobs are piling up under FIFO scheduling, diagnose and address the issue in two steps:
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Identify queued jobs: Open Logview and check the job's sub-status. A sub-status of Waiting for cluster resource means the job is waiting in the queue.
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Limit per-job resource consumption: Configure a maximum number of compute units (CUs) that a single job can use. This prevents one large job from monopolizing the quota group. For instructions, see Configure quotas.
Configure a scheduling policy
Prerequisites
Before you begin, ensure that you have:
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A level-1 quota of the subscription standard computing resource type
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Access to the MaxCompute console
Procedure
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Log on to the MaxCompute console and select a region in the top navigation bar.
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In the left navigation pane, click Quotas.
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On the Quotas page, find the level-1 quota to configure and click Quota Configuration in the Actions column.
NoteOnly quotas of the subscription standard computing resource type have the Quota Configuration option.
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On the Quota Configuration page, click the Basic Configurations tab, then click Edit Basic Configurations.
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In the Scheduling Policy column, select a scheduling method for the level-2 quota.
Scheduling policy Description Fair Distributes resources evenly across all concurrent jobs. Best when multiple jobs need to start and progress simultaneously. FIFO Allocates resources to the earliest-submitted job first. Best when you prioritize total pipeline throughput over individual job start times. -
Click OK.
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After the quota plan is configured, click Apply Immediately in the Actions column to activate the new configuration.
View the quota scheduling policy
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Log on to the MaxCompute console, and select a region in the top navigation bar.
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In the navigation pane on the left, click Quotas.
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On the Quotas page, click the
icon to the left of a level-1 subscription quota to expand the list of level-2 quotas. The current configuration information of the level-2 quotas is displayed. In the Scheduling Policy column, you can view whether the scheduling policy of a level-2 quota is FAIR or FIFO.