vIMS write-ahead data set (WADS) and IMS online log data set (OLDS)

vACBLIB for IMS

vBoot-strap data set (BSDS), the catalog and the directory for DB2

vDB2 logs

vAny essential non-database volumes

CICS applications can use non-DASD storage for processing data. If your application depends on this type of data, be aware that PPRC and XRC do not handle it.

For more information on PPRC and XRC, see Planning for IBM Remote Copy, SG24-2595-00, and DFSMS/MVS Remote Copy Administrator's Guide and Reference.

PPRC or XRC?

You need to choose between PPRC and XRC for transmitting data to your backup site. This topic compares the two methods to help you make your choice.

Choose PPRC as your remote copy facility if you:

vRequire data currency at the secondary site

vHave your recovery site within ESCON distance

vCan accept some performance degradation

vHave a duplicate DASD configuration available at the remote site

The synchronous nature of PPRC ensures that, if you have a disaster at your main site, you lose only inflight transactions. The committed data recorded at the remote site is the same as that at the primary site.

Use PPRC for high value transactions

Consider PPRC if you deal with high value transactions, and data integrity in a disaster is more important to you than day-to-day performance. PPRC is more likely to be the solution for you if you characterize your business as being low volume, high value transactions; for example, a system supporting payments of thousands, or even millions, of dollars.

Choose XRC as your remote copy facility if you:

vCan accept that your data at the secondary site will be a few seconds behind the primary

vHave your secondary site outside ESCON distance

vRequire high performance at the primary site

The asynchronous nature of XRC means that the remote site may have no knowledge of transactions that ran at the primary site, or does not know that they completed successfully. XRC ensures that the data recorded at the remote site is consistent (that is, it looks like a snapshot of the data at the primary site, but the snapshot may be several seconds old).

Use XRC for high volume transactions

Consider XRC if you deal with low value transactions, and data integrity in a disaster is less important to you than day-to-day performance. XRC is more likely to be the solution for you if you characterize your business as being high volume, low value transactions; for example, a system supporting a network of ATMs,

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IBM SC34-7012-01 manual Pprc or XRC?, Use Pprc for high value transactions