The easiest way to implement the IBM recommended layout is to assign your order's data sets to DASD volumes automatically, using the dialog's Create a Recommended System Layout function. This function helps you configure a target system that complies with the recommended system layout. The alternative is to assign data sets manually using either (1) the View and Change Data Sets by Selected Attributes function or (2) the Summary Display commands on the Modify System Layout Options panel.

As part of layout planning, decide whether you'll want to merge any data sets that have matching attributes in order to create a single panel library, single message library, and so forth. This is most easily done using the View and Change Data Sets by Selected Attributes option. See ServerPac: Using the Installation Dialog or SystemPac: CustomPac Dialog Reference for information about merging data sets in a ServerPac or dump-by-data-set SystemPac. Be aware that not all data sets that can be merged should be merged.

1. Back up the target volumes.
2. Check the names of data sets on the volumes. A data set name on a given volume must not be the same as the name of a data set that you plan to install on that volume. You can use the View and Change option of Modify System Layout of the CustomPac Installation Dialog to get a list of the data sets in your order.

   All data sets are initially allocated with one or more temporary high-level qualifiers, called system-specific aliases (SSAs). Later during installation, the data sets are renamed to remove these temporary qualifiers. If you plan to install your order using volumes that already have data sets on them, you must ensure that the names of the data sets already on the volumes will not be duplicated by the names of the data sets you will create, both with and without their temporary qualifiers.

1. Back up catalogs that will be updated by the installation process. You can use the Defining Alias-to-Catalog Relationships panel in the CustomPac Installation Dialog to determine which catalogs will be updated. Consider using a DASD backup utility such as DFSMSdss or the IDCAMS EXPORT TEMPORARY command. (But do not use the IDCAMS REPRO command. REPRO changes volume ownership for VSAM and SMS-managed data sets from the input catalog to the output catalog.) For information about DFSMSdss, see z/OS DFSMSdss Storage Administration and z/OS DFSMSdfp Storage Administration. For information about backing up catalogs using the EXPORT command, see z/OS DFSMS Managing Catalogs and z/OS DFSMS Access Method Services Commands.
2. Back up other operational data sets (like parmlib, proclib, and the primary RACF® database) that will be updated during the installation.
3. When using the CustomPac Installation Dialog's Modify System Layout function, make sure that the data set layout you specify matches your current system's catalog and volume structure (with the exception of new data sets that will be allocated as part of the installation and old data sets that you do not need to keep). The best way to do this is to use the saved configuration from your last order as the basis for the new configuration. The dialog does this by default, placing data sets on the same volumes with the same names. This makes it easy to keep the new system in sync with the old system's catalog and volume structure.

   If you cannot avoid changing the layout, you have to determine whether changes must be made to the existing system, and if so, how to make them. If the existing catalogs will never be used to IPL a system other than the new target, or the changes will not affect other systems that use the same catalog, you can change the existing configuration. However, if the existing catalogs will be used to IPL other systems and there is a possibility that users of those systems will be adversely impacted by the changes that the new catalog entries introduce, you must change your existing environment before performing the installation, change your planned configuration to make it compatible with your existing environment, or use new catalogs for the installation.

• Add the new entries to your existing catalogs and connect the new user catalogs to your existing catalogs.
• Update the new catalogs to use indirect and extended indirect catalog entries.