The READ subcommand

The READ subcommand reads the block specified by the RBA (relative block address) into storage and copies it into a work area.

This subcommand allows you to examine or change the database.

The syntax of the READ subcommand (of BLKUPD)

   READ rba [UPDATE]
            [NOUPDATE]

where:

rba

Specifies the relative byte address of the block to be read.

If the RBA does not represent an address on a 4KB boundary, the block on the 4KB boundary that contains the RBA is read. You can enter the RBA value as a hexadecimal (X'nn') or decimal (nnn) number. Hexadecimal numbers can be from 1 to 8 characters; decimal numbers can be from 1 to 10 characters.

UPDATE

Specifies you are planning to update one of the blocks in the RACF® database.

Specifying the UPDATE keyword imposes an exclusive RESERVE on the database, meaning that the issuing system has exclusive control of the RACF database and only that system can update it. Any system that shares the database cannot read the database or update it. In addition, no other user on the issuing system can read or update the database.

If RACF is enabled for sysplex communication:

You cannot update the RACF database when you are operating in read-only mode.
When running in data sharing mode, RACF uses global resource serialization (ENQ/DEQ), rather than hardware RESERVEs.

NOUPDATE

Specifies you are examining one of the blocks in the RACF database.

Specifying the NOUPDATE keyword imposes a shared RESERVE on the RACF database, meaning that if you are sharing the RACF database with another system, both systems can read the database, but neither system can update it.

The NOUPDATE keyword on the READ command permits you to examine the database block without making any changes. NOUPDATE is the default. Should you make changes and then end BLKUPD, the changes are not recorded.

If RACF is enabled for sysplex communication and running in data sharing mode, RACF uses global resource serialization (ENQ/DEQ) rather than hardware RESERVEs.