One thing almost everyone agrees on is that the IBM mainframe environment has a good handle on managing storage. In the mainframe, life-cycle management -- from data creation to deletion -- can be fully automated. When setting up a SAN environment and selecting storage management software (SMS), it is useful to keep in mind the features available in the mainframe environment.
Every file created in a mainframe SMS environment must have its name and the volume (LUN) where it resides placed in a system-wide catalog. In the case of a sysplex, this catalog can be accessed by up to 32 operating systems. The key feature of cataloging a file is that one point exists for locating, accessing and managing the file.
Additional information is stored with the file itself in structures on each volume. This additional information (metadata to use the current, in vogue term) defines how to manage the data. The general categories are data attributes, storage attributes and file management attributes.
Data attributes define what the file looks like. Some of the information includes the size of each record, the size of the file, whether the file resides on one or more volumes and the access method to be used to read or update the file.
Storage attributes define the performance desired for the file. This determines whether the file will be placed on solid state devices, high-speed disk or low-performance disk. For intelligent disk subsystems that support caching algorithms, these attributes also define the requirement for cache and, in some cases, the actual type of cache algorithm to be used. Availability needs, such as on-site or off-site disk mirroring for business continuance, can also be specified.
Management attributes describe the life cycle of the file. Creation date and retention period are required. If not supplied, a default retention period can be enforced. Backup requirements can be specified. Automatic movement of inactive files from high speed disk to an archival robotic tape subsystem can be requested or defaulted after so many days of non-use by a hierarchical storage management (HSM) product. Creation of off-site copies for disaster recovery purposes can be automated by selecting the proper management attributes.
Mainframe security can be added using either RACF or ACF. Both products integrate with the storage management software. Access to the file can be controlled at multiple levels: none, read, update, delete or alter (all the previous combined). The biggest flaw is that most of the security works at the file level, not the record level, although record level changes can be tracked and logged. Only some of the databases work with the security software for record and row level protection.
As noted above, the storage management software can use all these attributes to automatically manage a file from cradle to grave. Since this process is automated, it can scale easily to an almost unlimited number of files with no human intervention. Human actions can be limited to dealing with exceptions using one of the various exception reporting tools. Even clean up can be automated; a quick scan comparing volume contents to catalog listings can find invalid files left by job failures or someone trying to circumvent the rules. Most mainframe environments automatically delete these types of files.
When choosing storage management software for a LAN, these would be my minimum requirements. Other factors including ease of setup, ease of use and company specific needs would also be considerations. Choosing a storage management package with these features would be a good starting point.
About John Weinhoeft:
For the past 30-plus years John Weinhoeft has had his hand in the computer industry. He recently retired from designing and managing the State of Illinois' centralized computer systems that served 100 agencies. John has authored and edited a number of analytical books published by Computer Technology Research Corporation. He is, or has been, a member of several computer organizations including the Computer Measurement Group and Central Illinois Personal Computer Users Group.
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