Determining GDG Limit for Datacom RXX files

Products

• Datacom
• Datacom/AD
• Datacom/DB

Issue/Introduction

Datacom Started Task was created on March 16, 2025 with a GDG limit of 50 datasets for the spill job. Is there something to do to increase the size of the Log file/LXX Spill dataset (i.e., make it bigger) so that the Spill doesn't run so often?

Environment

z/OS

Resolution

First, you may be keeping more GDS for the RXX than you need.

The purpose of the RXX files created in the Spill job is to be able to recover your Datacom environment. This is typically done by running a DBUTLTY LOAD of a DBUTLTY Backup SEQ=PHYSICAL file taken before and as close to your problem event as possible. Then, you would apply the RXX files from that point forward to the current time.

For example, if your most recent BACKUP job was run Monday at 19.00, then you would restore that Backup file, and use all the RXX files from Monday 19.00 and forward. Therefore, you do not need any RXX files from before that time.

I also suggest that you run a SPILL as the first step of your BACKUP job, so the timings of the RXX and Backup files are close together.

Now, let's assume you are set up to take a Backup on a daily basis, and your Spill job runs about 4 times a day (the recommendation is to Spill between 2 and 4 times a day). In this scenario, I like to be conservative and set my GDG limit for the RXX files to hold 4 days' worth of file, so the Limit would be 16. In reality, I probably will never use more than the last 8, but this gives me a comfortable cushion.

We also recommend that you are using Automated operations processing to respond to certain messages in the MUF log in order to submit the Spill job. If you are not doing this, or if you have other questions about this, please have a look at Knowledge Base Article 26465, titled "Managing Datacom Log file (LXX) spills with automation (Automated Operations) routines." Additionally, if you want to better understand the relationship of the Backup and Spill process to the Forward Recovery process, please see Knowledge Base Article 279845, titled "Tips for Datacom Backups, Log Spills, and Forward Recovery."

Additional Information

As always, please contact Datacom support if you have any further questions on this.