Copying each file and directory of the aggregate to a larger data set
One method to increase the size of a zFS aggregate is to copy each file and directory of the
aggregate to a larger data set. Figure 1 shows an example of this
approach.
This approach uses the pax command to copy the individual files and
directories into an already formatted and empty zFS file system. Both file systems must be mounted.
pax uses the z/OS®
UNIX file and directory APIs to read and write each individual
file and directory of the hierarchy of the file system. (It does not copy lower mounted file systems
because of the -X and -M options.) You can use the ISHELL command
or the automount command with the allocany or
allocuser keyword to create the new larger aggregate to copy into with
pax, because they format the aggregate.
If you are running this job on a system that is running z/OS V1R13 or later, and the file
system was written to using a prior release of z/OS, zFS might use more DASD space for the
same data than it did on the prior release. The increase in DASD space
can occur for small files (1 KB in size or less) because beginning
with z/OS VR13 zFS does not
store data in 1-KB fragments; instead, it stores data in 8-KB blocks.
For example, if the file system contained 1000 files that are 1 KB
in size, zFS on z/OS V1R13 or later could use a maximum of 10 cylinders
more than on previous releases. You can determine how many files are
in the file system that are 1 KB or less by using the following z/OS UNIX command:
find mountpoint -size -3 -type f -xdev | wc -l
After you successfully copy the data, when you are comfortable with the new, larger aggregate, you can delete the old aggregate.