(zos)

Switching between 64 and 31 bit modes

When creating a new application server, it is automatically configured to run in 64-bit mode. We can deselect the Run in 64 bit JVM mode setting if we need to run the server in 31-bit mode. Whenever possible, however, leave the servers configured to run in 64-bit mode because support for running servers in 31-bit mode is deprecated. If we have any servers, that you migrated from a previous version of the product, that are running in 31-bit mode, consider reconfiguring them to run in 64-bit mode.

Deprecated feature: Because support for running a server in 31-bit mode is deprecated, whenever you start a server configured to run in 31-bit mode, you receive the following message in the system log, where server_name is the name of the server running in 31-bit mode:

depfeat

When a server runs in 31-bit mode, the following conditions exist:

When a server runs in 64-bit mode, the following conditions exist:


System requirements

Before starting to use a server configured to run in 64-bit mode, note that:

For more information, see the following z/OS publications:


Converting a migrated server to run in 64-bit mode

Before converting an application server from 31-bit to 64-bit mode...

To convert an application server from 31-bit mode to 64-bit mode, in the console select the Run in 64 bit JVM mode option on the configuration settings page for that application server, and change the minimum and maximum JVM heap sizes to values that are appropriate for a 64-bit process. Similarly to convert an application server from 64-bit mode to 31-bit mode, deselect the Run in 64 bit JVM mode option on the configuration settings page for that application server, and change the minimum and maximum JVM heap sizes to values that are appropriate for a 31-bit process.

If we use the MVS START command to start a 64-bit server, make sure that the AMODE parameter is set to 00 or 64, or is allowed to default to 00, on the START command. For example, you might issue one of the following commands:

S BBO7ACR,JOBNAME=BBOS001,ENV=BBOBASE.BBONODE.BBOS001,AMODE=64

S BBO7ACR,JOBNAME=BBOS001,ENV=BBOBASE.BBONODE.BBOS001

The startServer.sh command, and the console, automatically add the AMODE=64 parameter when they are used to start a 64-bit application server.


Converting a migrated deployment manager to run in 64-bit mode

Before converting a deployment manager from 31-bit to 64-bit mode...

To convert a deployment manager from 31-bit mode to 64-bit mode, go to Servers > Server types > WebSphere application servers > server_name in the console and select the Run in 64 bit JVM mode option on the configuration settings page for the deployment manager as well as change the minimum and maximum JVM heap sizes to values that are appropriate for a 64-bit process.

If we use the MVS START command to start a 64-bit deployment manager, verify the AMODE parameter is set to 00 or 64, or is allowed to default to 00, on the START command. For example, you might issue one of the following commands:

The startServer.sh command and the console automatically add the AMODE=64 parameter when they are used to start a 64-bit deployment manager.


Converting a server to run in 31-bit mode

Before converting a server from 64-bit to 31-bit mode, verify that all applications to run on the server use 31-bit native code and DLLs.

To convert a server from 64-bit mode to 31-bit mode...


Related

  • Java virtual machine settings


    Related information:

    z/OS Publications
    64-bit Addressing Support
    C/C++ Code Considerations With 64-bit WebSphere Application Server for z/OS