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WebSphere Application Server for z/OS Frequently Asked Question

Document Author:

Don Bagwell

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WebSphere Application Server for z/OS

FAQ: How big should my /tmp directory be for WebSphere on z/OS?

Answer to this FAQ:

2009, IBM Washington Systems Center
Americas Advanced Technical Support
WebSphere on z/OS makes additional use of the /tmp directory and the filesystem that supports it. It may be necessary for a customer to increase the size of the filesystem before attempting to configure WebSphere on z/OS. One of the symptoms of a "too small" filesystem for /tmp is a failure install an application properly caused by a failure to copy the .ear file into the /tmp directory.

One way to determine the size of the filesystem is to enter ISHELL in ISPF at the root "/" level and use the line command "U" on the line for /tmp. This will display a box with information on the filesystem. Multiplying the "Block Size" field by the "Total Blocks" field will yield the total space in the file system in bytes. Multiplying the "Block Size" field by the "Available Blocks" field will yield the available space in bytes. An alternative way is to issue the “df –k .” command from within any shell (telnet, ssh, OMVS…). This will produce a couple of lines similar to:

-> df -k .

Mounted on Filesystem Avail/Total Files Status
/SYSC/tmp (SYSC.TMP) 204656/204800 51164 Available

Examining the number displayed for Total Kbytes above indicates that the /tmp filesystem in this case had been defined as 200 Megabytes (204800/1024=200).

Many applications now are contained in very large .ear files. The HATS development tool in particular generates .ear files which have exceeded 100 megabytes. Deployment of these application requires a large /tmp filesystem. If the /tmp filesystem cannot accommodate both a copy of the .ear file and the exploded (unzipped) components contained within it, then deployments will fail, and action must be taken to increase the amount of available space.

If the filesystem is an HFS (non-temporary) then the filesystem must be unmounted, deleted and reallocated with a larger amount of space, and remounted.

If the filesystem is a TFS (temporary filesystem) which is essentially a memory resident file system, the filesystem must be unmounted, and remounted with more space. A sample mount command might be:


The value following the "-s" in the PARM field is the amount of space in megabytes, in this example 500. The default if the PARM field is omitted or incorrectly specified is 1 megabyte, which is clearly too small for this application.

A reasonable suggested size for the /tmp filesystem would be 1 gigabyte (a parm of ‘-s 1000’).

More information on TFS specification is available in Chapter 14 of the z/OS V1R10.0 UNIX System Services Planning (GA22-7800-14) manual.




Installation and Migration


IBM System z Family

S/W Pillar(s):





WebSphere, HFS, TMP, TFS

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