Mainframe, MVS and zOS Discussion

Hi,

I had this problem:

To an existing dataset, I needed to allocate a BIG storage. This dataset is not created anywhere in some Job where I could modify SPACE parameter. Unfortunately, yesterday there was a huge in flow of number of records records written to this dataset and we got an abend for this.

I'm thinking if I can dynamically allocate the space and release the rest, is this possible?

To solve this, I did the following:

I was not able to figure out how to do it dynamically. So, I had to delete the dataset, created a new one with same attributes and used a higher SPACE. But is there any other better way to do it?

In general, JCL does not support dynamic space allocation -- if you are talking about the space going up and down depending upon the number of records. z/OS uses high-water-mark allocation where the data set will reflect the largest number of records that have ever been in the data set. However, sites can (and often do) use a tool that frees unused space in data sets; check with your site support group to determine if you site does use such a tool.

Your best long-term solution will probably be to ensure there are some extra volumes available for the data set and change the allocation to have a relatively large secondary allocation so if a large number of records are placed in the data set again the space allocation will give enough space.