If USEDSSIO is set to HWCOMPR, does this include all data sets with the SMS Dataclass parameter Compaction = Y , T, G, ZR, ZP ?

Document ID : KB000015851
Last Modified Date : 14/02/2018
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Introduction:

As per IBM documentation, the SMS Dataclass parameter Compaction can be set to: 

 

Y - Extended format data sets are compressed and tape volumes are compacted, but the type of DASD compression depends on the COMPRESS option in the IGDSMSxx PARMLIB member. 

T - Extended format data sets are compressed using tailored dictionaries. 

G - Extended format data sets are compressed using generic dictionaries. 

ZR - Indicates "zEDC Required", meaning that the system should fail the allocation request if the zEDC function is not supported by the system, or if the minimum allocation amount requirement is not met. 

ZP - Indicates "zEDC Preferred", meaning that the system should not fail the allocation request, but rather create either a tailored compressed data set if the zEDC function is not supported by the system, or a non-compressed extended format data set if the minimum allocation amount requirement is not met. 

 

T, G, ZR, and ZP override the compression option set in the IGDSMSxx PARMLIB member, and let you select the type of compression on a data set level. 

 

 

Question:

If CA Disk system parameter USEDSSIO is set to HWCOMPR, does this include all data sets with the SMS Dataclass parameter Compaction = Y , T, G, ZR, ZP ?        

Answer:

The CA DISK parameter USEDSSIO HWCOMPR takes into account all Compression Types that can be specified in a Dataclass and invokes DSS, but we do not pass any compress parameters to DSS.