Addressing storage requirements

Roles required: storage administrator, system programmer

Ensure that you have sufficient storage depending on the installation method. Review the storage requirements according to your installation method as presented in this article.

Installing Zowe Server Runtime

Before installing Zowe, review the reference for Zowe's server datasets

Installing with SMP/E

Additionally, when installing Zowe with SMP/E, review the DASD storage requirements.

Memory requirements for API Mediation Layer

Before placing limits on available system memory to Zowe API ML, it is necessary to consider resource consumption. The memory consumption depends on specific use cases and network traffic.

The main type of memory used by Java applications, including Zowe API ML components, is heap memory. Heap memory is defined by the initial and maximum memory size. Each Zowe API ML service uses a default minimum of 32 MB and a maximum of 512 MB. When a service requires more memory, the service allocates additional memory in increments of the same size as the initial memory. When the system has limited resources, it is a good practice to set a fixed minimum and maximum memory size. Memory is then allocated during startup, preventing the memory from exceeding the specified limit.

The following table shows the expected heap memory requirements for core Zowe API ML services:

Component name	Memory usage
Gateway Service	512MB
ZAAS	128MB
Discovery Service	128MB
API Catalog	128MB
Caching Service	256MB

JVM Memory

Different memory types are used by JVM services: native, threads, direct memory buffers, and JIT (just-in-time compilation).

Direct memory buffers are limited to the same size as heap memory. By default, in the case of large network traffic, the JVM can allocate up to the same memory allocation as applied to heap memory.

Similarly, threads responsible for processing incoming requests are prepared during JVM start-up. By default, 20 threads are available to process incoming requests. Additional threads can be created on demand (up to 200 threads by default). When the system has limited address space, it is recommended to use fixed-size thread pools, initializing all threads at the beginning.

As a general rule, total memory consumption should be 150% of the heap size.

Customizing memory limits in Zowe API Mediation Layer

Setting memory limits strictly depends on the use case, such as the kind and volume of data that is typically transferred, how many users can be active simultaneously, and the number and type of onboarded services.

If limits need to be set, it is recommended to verify your environment with the following procedure:

1. Run the API ML without a memory limit.
2. Start the services you wish to start and wait approximately an hour or until you have the expected level of traffic to the service.
3. Assess the memory usage during a typical workload.

Setting a direct memory buffer limit

To set a direct memory buffer limit, set the following property: zowe.environments.JAVA_OPTS: -XX:MaxDirectMemorySize=<value><k|K|m|M|g|G>

• <value><k|K|m|M|g|G>
  Specifies the limit size and unit.
  Example: 64M is a 64 Megabyte limit.

Establishing a fixed thread pool

To establish a fixed thread pool, set the following properties to the same value:

• zowe.environments.SERVER_TOMCAT_THREADS_MIN_SPARE
  The initial number of threads
  Default: 20 threads to process incoming requests.
• zowe.environments.SERVER_TOMCAT_THREADS_MAX
  The maximum number of threads
  Default: Up to 200 threads

Note: Updating these environment values impacts all Java-based services running as part of the Zowe Server.

The following example shows the configuration of all applicable parameters:

Example:

zowe:
  environments:
    SERVER_TOMCAT_THREADS_MIN_SPARE: 100
    SERVER_TOMCAT_THREADS_MAX: 100
    JAVA_OPTS: "-XX:MaxDirectMemorySize=64M"

components:
  gateway:
    enabled: true
    heap:
      init: 256
      max: 256
  discovery:
    enabled: true
    heap:
      init: 256
      max: 256
  api-catalog:
    heap:
      init: 512
      max: 512
  caching-service:
    heap:
      init: 512
      max: 512
  zaas:
    heap:
      init: 256
      max: 256

tip

It is recommended to set REGION=0M in the STC, which is the default setting. Setting a MEMLIMIT is not recommended as doing so prevents issues caused by insufficient memory.

For more details about specifying the region size, see the following links:

• Specifying Region Size in the IBM documenation
• Address space region size in Zowe Docs
• Resources in the article Installing Product Software Using z/OSMF Deployments in Zowe Docs

When setting a memory limit, consider all running Zowe services, the typical workload, and a buffer to the memory requirement.