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How to Capture Wasted Cartridge Space in z/OS

1. ALP 16 lt ALP 15 9 ALP 11 gt ALP 12 gt ALP 13 gt ALP 14 gt ALP 8 ALP7 ALP 6 ALP5 ALP 1 gt ALP 2 ALP 3 gt ALP 4 Figure 8 partition numbers 0 9 and 10 are written in section 0 If users desire to set a write mask for an entire section the mask table below can be referenced for the binary values For any section the mask values are a repeating binary sequence indicated by the values show in the table below For example To mask the entirety of section 0 as writable a writable mask containing 60 bytes with the hexadecimal values of 80 60 18 06 01 80 60 18 06 01 should be written to the drive Drive Operation The following picture is taken from the Tape Tiering Accelerator example For the discussion of drive operations users can refer to Figure 9 It also may be helpful for users to refer to the Tape Tiering Accelerator example to see how the tape got into this condition Files ALPs 2 3 4 6 7 9 10 14 15 Figure 9 Three different logical volumes with ALP Logical Volume A logical volume is defined as a Tape Tiering Accelerator group in which instances are linked together that have both a block 0 and a physical EOD In the above figure there are two complete logical volumes The first logical volume maps partition numbers 2 3 4 9 and 10 files M and N and the second logical volume maps partition numbers 7 8 15 a
2. Partitions are enabled for read only all partition bytes are set to zero This is the default state when a Tape Tiering Accelerator tape is loaded When issuing the TTA partition map command the tape must be positioned at beginning of tape BOT otherwise command reject status is returned Locate Tape Tiering Accelerator Partition Command X BF 2 byte parameter data How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator The locate TTA command moves the tape into position on the target tape drive so that the application can write or read on a specific partition on tape The tape drive positions the tape to the nearside of the first block of the partition This command requires a data length of 2 with the parameter data containing a 2 byte binary partition number 0 479 A Tape Tiering Accelerator formatted tape must be loaded and ready if any of these conditions are not true a command reject ERPA_code 27 will result Initial status of channel end CE will be presented and device end DE will be presented upon the command s completion The 2 byte parameter data will be boundary checked and a command reject CR will be issued if the value is outside the boundary supported by the loaded tape Once the tape is located to a partition then normal commands such as write read tape mark sync read RBID and so on are used to process the blocks within the partition The RSSD command is us
3. RSSD3590 EQU x 40 3590 Emulation RSSDVLSE EQU x 80 Volsafe Enabled RSSDPART DC XL2 0 TTA Partition Number RSSDRSV3 DC XL6 0 Reserved RSSDCAP DC XL1 0 Drive Capibilities RSSDRS1F EQU X O1 Reserved RSSDTTAF EQU X 02 TTA Capable RSSDRS4F EQU xX 04 Reserved RSSDBTMF EQU X 08 Write Buffered TM RSSDSRAF EQU LO Stop Read Ahead RSSD349F EQU X 20 3490 Capable RSSD359F EQU x 40 3590 Capable RSSDVLSF EQU x 80 Volsafe Capable RSSDRSV4 DC XL8 0 Reserved RSSDHOST DC XL1 0 Host Type ID RDDSRSV4 DC XL10 O Reserved RSSDSIZE EQU RSSDMAP Size of area 17 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator Conclusion The Tape Tiering Accelerator feature of Oracle s StorageTek T10000C tape drive helps users capture wasted space that is caused by data set expiration Tape Tiering Accelerator is preferred to reclaiming tapes because it takes far less time thus reducing labor cost increasing access times and enabling more efficient use of tape capacity Additionally the tape drive handles much of the formatting without host intervention This white paper instructs users in z OS environments about the use of Tape Tiering Accelerator which creates automatically linked partitions so the data can span tiers or partitions and be noncontiguous on tape 18 ORACLE How to Capture Wasted Cartridge Space in z OS Implementations U
4. such as labels followed by a nonbuffered tape mark 5 Optionally detect current TTA state may be performed and the TTA mode bit will be set but the Tape Tiering Accelerator cartridge bit will not be set until the tape is reloaded At this point the tape is a Tape Tiering Accelerator formatted tape and the map TTA partitions and locate TTA partition can be used to map and position the tape to the desired partition Normal I O command processing is available to process the tape In some cases general utilities may or may not work once a Tape Tiering Accelerator formatted tape is loaded and positioned to a partition greater than 0 Start New Logical Volume To start a new logical volume a Tape Tiering Accelerator formatted tape must be loaded or created Each partition potentially can be a standalone 9 68 GB logical volume or multiple partitions contiguous or noncontiguously linked to form a logical volume 1 Map TTA partitions described in section 2 3 partition 0 must be set to write This step may have been performed already it only needs to be done if the map needs to be changed 2 Locate TTA partition described in section 2 4 to position the tape at the start of the new logical volume 3 Write at least one block and nonbuffered sync or one nonbuffered tape mark Any number of blocks can be written such as labels followed by a nonbuffered tape mark Convert a Tape Tiering Accelerator Tape to Standard Tape Command X 77 sub
5. M reclaims the space that file B used to occupy Normal Spacing and Locating In figure 10 if the user can locate to any blocks in the range of 0 through 29 999 It is no problem because the partition instances are linked If the user locates to 10 000 then the tape will end up in partition 1 UC into EOD Example Figure 10 shows files A B and C Partition numbers 0 1 2 are all linked together into one logical volume As shown the EOD is at the end of partition 2 In figure 11 file B expires at the host In Figure 12 the host reclaims partition 1 When that reclaim occurs the links are broken and each partition has its own EOD If the user now tries to locate to block 10 000 then the tape drive will generate a crash into EOD because partition 0 is no longer forward linked to partition 1 UC into BOT Example 13 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator Figure 10 shows files A B and C Partition numbers 0 1 2 are all linked together into one logical volume As shown the EOD is at the end of partition 2 In Figure 11 file B expires at the host In Figure 12 the host reclaims partition 1 When that reclaim occurs the links are broken and each partition has its own EOD If the user locates to partition 2 with the locate TTA command then the tape drive will be positioned in partition 2 Now if the user tries to locate to block 10 000 then the tape drive will generate a UC
6. louie EEE aidan een E E res 12 Spacing and Locating crire irere eee rak 12 Tape Tiering Accelerator LayOut ssssssssssssssssssssssssssssssseseees 14 Tape Tiering Accelerator Capacity ccccceeeceeeeeeeeeeeetteeeeeeeeeeteees 14 Potential Tape Tiering Accelerator Benefits and Effects 14 Increased ACCESS TiM S ccccccceeeeeeeeeeeeeeeeeeeeeeeeeesensnaaeeeeeees 14 Efficient Use of Tape Capacity cccccccceeeeesssseseceeeeeeeeteeeesnaeees 14 EIA Or ODGT ALOIS ttn ht Otte Os E ht 14 Initializing a Tape Tiering Accelerator Tape eeeeeeeeeeeeees 14 Loading a Tape Tiering Accelerator Tape cccccceeeeeeeeeeeeeeeees 15 Positioning to a Host File sicc 4 cas acvesassccsdsasassesass lt lxcsaasaiseasaseusassee 15 Reading a Host Filensmniinninni neant eiie 15 Appending a Host File asec cance vy estan donsnetvesnse acne etseatevecaeteets 15 Writing a Host File to a Free Tape Tiering Accelerator 15 Tape Tiering Accelerator Data Definitions sssseeeeeeeeeeeees 16 COMCIUISION ate eee ete ae et mE 18 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator Introduction Tapes hold hundreds to thousands of gigabytes of data Typically the data is stacked on the media as different data sets and each data set has a different expiration When the expiration occurs there is wasted space on the tape Ov
7. KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK Copyright c 2011 Oracle and or its affiliates All rights reserved Dsect map for RSSD information returned for Generic Host X Revised 6 01 2011 8 kkxkxkxkxkxkxkxkxkx xkxkxkxkxkxkxkxk xkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxkkxkxxkxx k a RSSD Map RSSDMAP DSECT RSSDLEN DC XL2 0 Length of this RSSD Message RSSDMID DC XL1 0 Message ID RSSDNMSG EQU xX 00 No Message RSSDIDST EQU xr 02 ID Status RSSDSTK EQU X EO STK Message ID RSSDMCD DC XL1 0 Message Code RSSDMCD1 EQU X OLS Dependent Format RSSDMSGI DC XL4 0 Message ID RSSDFLG1 DC XL1 0 Flag Byte 16 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator RSSDNNS EQU KTOL Notify Non supported RSSDSOLM EQU X 02 Solicited Message RSSDRSV2 DC XL5 0 Dependent on format and msg code RSSDCART DC XL1 0 Cartridge Status RSSDTTAC EQU X 02 TTA Cartridge is loaded RSSDVOLS EQU X 80 Volsafe Cartridge is loaded RSSDFET1 DC XL1 0 Drive Enabled Features RSSDRBIE EQU X O1 Reserved RSSDTTAE EQU X 02 TTA Drive Mode is Enabled RSSDRB4E EQU X 04 Reserved RSSDBFTM EQU X LOGT Buffered Tape Marks RSSDSTRA EQU xX 10 Stop read Ahead RSSD32BI EQU X 20 3490 32bit BlockID Emulation
8. STORAGETEK An Oracle White Paper April 2014 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator ORACLE How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator PME OGG ICI PE EE E roe astacscwasudns sams lecuueeskeesaaastedeuseccensae mba T 1 Tape Tiering Accelerator Programming Methods for Z OG 5 3 SL OSE TV BG ven tess sccanary sca tcaubasquas ba catuataseaquangtlaadav bsbea uaa a tans 3 Detect Current Tape Tiering Accelerator State 0 cee 3 Map Tape Tiering Accelerator Partitions cccccccccceceesceeeeeeeees 4 Locate Tape Tiering Accelerator Partition cccccccccceseeeeeeeeeeees 4 Report Tape Tiering Accelerator Linkage cccccceeeeeeeeeeeeeeeeeees 5 Create Tape Tiering Accelerator Tape sssssssssssseseesseeeeseees 5 Start New Logical Volume sii seisnisnesc ganas len cine nt ndetigenennadacunendecpueden 6 Convert a Tape Tiering Accelerator Tape to Standard Tape 6 Tape Tiering Accelerator EXAmples ssssssssssssssssssssssssssseeeeeees 7 STENS Se 1o ee ean URE E RMR at ae PE ae en ROPE aE eet EA 7 lMBTOVe ACCESS nanna a a E a atiNenes 9 Drive Op rati N sie e aaa E an a ae aeaii 11 togical WOM Seis ce scents cated E a a E E e sees 11 Partial LOGICAL Volume mnene i 11 V RO ieee en aa ene a a ec ee eA 12 PRCA CUIIG sarees deisdarcesatterusadusiepectereuasacdss
9. ch point the drive returns EOD Spacing and Locating The drive operates on partial logical volumes when processing space block file and locates commands When spacing locating prior to first block in a partial volume the drive reports back that BOT has been crashed For example if record G in partition 11 starts at block 10 000 then any operation that ends up before 10 000 reports a unit check UC BOT Similarly when spacing locating beyond the last block in a partial volume EOD is reported For example if record E in partition 8 ends at block 1 500 then any operation that ends beyond 1 500 reports a UC EOD 12 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator Figure 3 and Figure 5 serve as examples In Figure 3 file A starts in partition 0 and for this example the starting block ID for partition 0 is zero File B spans partition 2 and for this example the starting block ID in partition 2 is 20 000 Now file B expires In Figure 5 the user decided to write file M starting in partition 2 The result of putting file M into ALP 2 caused an EOD to be put down at the end file A Starting block Files TTAs Figure 10 Three files written into one logical volume P Starting block Files TTAs Figure 11 File B expires but nothing has reclaimed that space yet Starting block Files TTAs Zo a a EOD EOD EOD Figure 12 File
10. ck ID RFID Positioning to a host file is as easy as issuing a locate TTA command to the proper partition and then issuing a standard tape locate command to get to the start of the host file Tape Tiering Accelerator tape read position byte level references are relative to a start of volume position for a particular partition If for example a second or third partition is created at partition 10 by issuing a start volume at that partition 10 then once a file is written beginning at tape partition 10 any subsequent read position information RFID for that partition will be relative to the volume beginning at partition 10 The same is true regardless of how many pattitions are created Issuing a start volume at a particular partition does not immediately set the beginning RFID to RFID 0 a write to that volume must occur first Reading a Host File After positioning to a host file reading is a simple as issuing standard tape read commands the drive will automatically transition to next partition instances as needed Appending a Host File When users append a new host file to an existing one the host will first position the drive to the end of the existing host file Next the host should issue a detect current TTA state command sequence and note the value at bytes 16 to 17 in the host s file location structure Next the host should issue a standard read position command to get the RFID this also should be noted in the host s file location
11. cribes the steps required to create a Tape Tiering Accelerator tape from a standard tape After the required steps are completed the tape is formatted as a Tape Tiering Accelerator tape with a logical volume starting at Tape Tiering Accelerator partition 0 The drive will recognize the tape as a Tape Tiering Accelerator tape when it is loaded A Tape Tiering Accelerator formatted tape cannot be processed as a standard tape once formatted as a Tape Tiering Accelerator tape z OS will detect a permanent I O error during open Additionally How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator when a Tape Tiering Accelerator tape is created from a standard tape it is necessary to bypass label processing by specifying BLP on the DD label parameter or by using other means Once the drive is loaded and ready and the tape is at beginning of tape BOT the following sequence of commands can be performed 1 Set host type described in section 2 1 to allow the Tape Tiering Accelerator commands to be recognized 2 Detect current TTA state described in section 2 2 to verify that the drive is Tape Tiering Accelerator capable and a standard not Tape Tiering Accelerator is loaded and the TTA mode bit should be zero 3 Map TTA partitions described in section 2 3 partition 0 must be set to write 4 Write at least one block and nonbuffered sync or one nonbuffered tape mark Any number of blocks can be written
12. cular tape is old not needed data This data now can be reclaimed without having to rewrite the valid data on the tape With tape capacities ever increasing the effective tape capacity will continue to worsen Theory of Operation While there are many valid ways to use the set of commands to perform an individual application s requirements this section shows how Oracle envisioned the use of the commands Initializing a Tape Tiering Accelerator Tape 14 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator To initialize a Tape Tiering Accelerator tape the only requirement is to issue the create TTA tape command sequence on a tape that is in the free pool it is important to know that the activate process is destructive Best practices also set the writable partitions mask for byte 0 bit 7 to a logical 0x1 and recommend writing some sort of label or tape mark at partition 0 Partition 0 must be initialized before volumes that utilize remaining partition instances may be created or accessed Loading a Tape Tiering Accelerator Tape After loading a Tape Tiering Accelerator tape a map TTA partitions command should be issued so the tape can be written The writable mask is kept by the host application based on which partition instances no longer hold valid data Positioning to a Host File The host is responsible for keeping track of where each host file is on tape in the form of partitions and blo
13. dge Space in z OS Implementations Using Tape Tiering Accelerator is for illustration purposes only The actual StorageTek T10000C tape drive ALP format has 480 instances of partitions and is too large to show in a small drawing In this illustration Tape Tiering Accelerator 0 is located at the beginning of tape BOT at the bottom left side and the ALPs serpentine through the tape in a linear fashion from BOT to end of tape EOT and back again Section 0 Section 1 Section 2 Section 3 Section 4 lt ALP 39 ALP 38 lt ALP 37 lt ALP 36 lt ALP 35 ALP 30 gt ALP 31 ALP 32 ALP 33 gt ALP 34 ALP 29 ALP 28 lt ALP 27 lt ALP 26 lt ALP 25 wo ALP 20 ALP 21 ALP 22 ALP 23 gt ALP 24 m Q ALP 19 ALP 18 ALP 17 ALP 16 lt ALP 15 9 ALP 10 gt ALP 11 gt ALP 12 gt ALP 13 gt ALP 14 gt ALP 9 ALP 8 ALP7 ALP 6 lt ALP5 ALP 0 gt ALP 1 gt ALP 2 gt ALP 3 gt ALP 4 gt Figure 7 Representation of a Tape Tiering Accelerator formatted tape Section 0 in Figure 7 contains partition numbers 0 9 10 19 20 29 30 and 39 Since all of these are in a single section the average access time to locate to any partition in section 0 is relatively short A StorageTek T10000C tape drive has an average access time of approximately 10 seconds for any partition in the same section If the application requit
14. e any other Tape Tiering Accelerator commands will be recognized Detect Current Tape Tiering Accelerator State Command X 77 suborder X18 12 byte parameter data prep for RSSD Command x 3B 40 byte buffer to receive RSSD response chained to prep for RSSD The RSSD command is used to return the Tape Tiering Accelerator state of the StorageTek T10000C tape drive and loaded tape The detect current TTA state command indicates the following about the tape drive Tape Tiering Accelerator capable Tape Tiering Accelerator enabled Tape Tiering Accelerator tape loaded and current partition number at which the tape is positioned To issue this command the correct host type command must have been issued and the RSSD channel command How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator word CCW must be chained to a PSF command with the prep RSSD parameter data specified The PSF command must be the first CCW in the chain Prep for RSSD parameter data supplied X 180000000000030000000000 The RSSD command returns the following Tape Tiering Accelerator related status fields e Byte 14 Cartridge status X 02 indicates and Tape Tiering Accelerator formatted cartridge e Byte 15 Drive status X 02 indicates the drive is in Tape Tiering Accelerator mode e Byte 16 17 2 byte current partition position e Byte 24 Drive capability X 02 indicates the drive is Tape Tiering Accelerato
15. ed to return the current partition the current partition is relative to blocks actually written on the physical tape A SYNC command will flush the cache to tape in order to obtain an accurate Tape Tiering Accelerator partition number Report Tape Tiering Accelerator Linkage Command X B2 return 2048 bytes of information The report TTA linkage command returns the current Tape Tiering Accelerator mode tape linkage mapping The command returns 2 048 bytes of information The information represents how the partitions are forward linked together The information represents each of the partitions 2 bytes of data for each partition The 2 bytes of data are the next partition number in the link or one of four special values The four special values are X FFFF Partition not linked or no more Tape Tiering Accelerator partitions linked to this partition X FFFE Partition not used or the Tape Tiering Accelerator partition isn t used in the current tape format X FFFD Partition link unknown or the drive doesn t know if the Tape Tiering Accelerator partition is linked to something else This only happens when a tape is loaded and the drive is power cycled or receives an unexpected reset condition X FFFC Partition blank or the Tape Tiering Accelerator partition hasn t been written since the last time the tape was converted to a Tape Tiering Accelerator tape Create Tape Tiering Accelerator Tape This section des
16. er time the wasted space becomes so large that customers must reclaim the tape which can consume many hours In order to save these customers time and money Oracle created a method to capture the wasted space the Tape Tiering Accelerator feature of Oracle s StorageTek T10000C tape drives The tape drive creates a hard disk like format so that more of the tape can be used Tape tiering or partitioning nonlinked has existed for many years however many current tape drives don t implement them because developers didn t think it was useful This implementation goes beyond tiers and creates automatically linked partitions so the data can span tiers or partitions and be noncontiguous on tape Furthermore the tape drive handles much of this formatting without host intervention The StorageTek T10000C tape drive Tape Tiering Accelerator specifications e Cartridge requirement Long Fuji e Number of partitions 480 e Partition size 9 GB This paper describes how z OS users can format a Tape Tiering Accelerator cartridge and access it but it does not detail how to manage the partitions or the data in them The StorageTek T10000C tape drive does not store read write access status of partitions but it does store the logical volume start and linkage status in the media information record MIR When the term automatically linked partition ALP is mentioned in the paper it is synonymous with Tape Tiering Accelerator How to Capture Wasted Cartr
17. es fast tape access this can be achieved with the construction of logical volumes within the same section To build a logical volume in section 0 the following commands should be sent to the drive 1 Load a StorageTek T10000C tape drive ALP formatted tape 2 At BOT issue a set writeable TTAs command sequence that maps partition numbers 0 9 10 19 20 29 30 and 39 3 Issue a start new logical wolume command sequence 4 Begin writing this logical volume As files are written to this logical volume the drive will automatically link the mapped partition instances starting with the lowest numbered ALP If application files are written to the first three partition instances in the logical volume to the partition instances shaded in yellow will contain the logical volume as shown below A wrap turn will be performed at the end of partition 0 and partition 9 will be written in the opposite direction At the end of partition 9 another warp turn will be performed and direction reverses again 10 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator Section 0 Section 1 Section 2 Section 3 Section 4 ALP 39 ALP 38 ALP 37 ALP 36 lt ALP 35 ALP 30 gt ALP 31 gt ALP 32 ALP 33 gt ALP 34 gt ALP 29 ALP 28 ALP 27 ALP 26 lt ALP 25 wo ALP 20 gt ALP 21 gt ALP 22 ALP 23 ALP 24 gt m o lt ALP 19 ALP 18 ALP 17
18. es that are written to tape expire and become obsolete or invalid As the expired files become obsolete the tape begins to resemble Swiss cheese with holes created throughout the tape In Figure 4 host files B and F expire and become obsolete which frees partition numbers 2 3 4 9 and 10 for space reclamation Files Expired Expired ALPs Figure 4 Host files becoming invalid The application now can reuse the instances of partitions containing the expired files by starting a second logical volume and overwriting them Initially the application should execute a new set writeable TTAs command sequence that maps partitions 2 3 4 9 and 10 as writeable Then the application positions to the first partition that was freed when record B expired In this case it is partition 2 To locate to partition 3 the locate TTA command is used The application now can write files M and N As these files are written to tape the drive automatically positions to the next available partition This process may occur over multiple mount and dismount cycles and across several drives Although read access is still permitted to all instances of partitions it is possible to write to partitions that form the current writable instances of partitions 2 3 4 9 and 10 shown as green blocks below File N links from partition 4 to partition 9 and then continues into partition 11 The space between file A and M end of partition 1 N and C beginning of par
19. files D and H shown in Figure 5 expire Following the same process as described above the application now can start a third logical volume purple Again users start by sending a new set writeable TTAs command sequence that maps partitions 6 7 14 and 15 a locate TTA command to Tape Tiering Accelerator number 6 As shown in Figure 6 the host then can write this third logical volume with files S and T Figure 6 New files written for third logical volume To read the second logical volume green in Figure 6 1 Locate to TTA 2 2 Read files M and N To read the third logical volume purple in Figure 6 1 Locate to TTA 6 2 Read files S and T It is worth noting that the application only needs to track the partition number and host block ID when space for expired files is reclaimed and used by another logical volume In logical volumes that have not had space reclaimed like the green and purple examples in Figure 6 the Tape Tiering Accelerator feature of the tape drive will move from partition to partition as if the logical volume was written sequentially in a single tape partition Improve Access This example describes features that are only supported in the StorageTek T10000C tape drive The following representation of a Tape Tiering Accelerator formatted tape has five sections with five instances of partitions in each section for a total of 25 ALPs This format does not actually exist and it How to Capture Wasted Cartri
20. idge Space in z OS Implementations Using Tape Tiering Accelerator How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator Tape Tiering Accelerator Programming Methods for z OS The StorageTek T10000C tape drive introduces a new set of command codes and extensions to other command formats on z OS To implement these command codes the use of EXCPVR is required EXCPVR is documented in the following IBM publications e SC26 7400 DFSMSdfp Advanced Services e SC26 7408 Z OS Macro Instructions for Data Sets e SA22 7605 MVS Programming Assembler Services Guide In Figure 1 the Tape Tiering Accelerator tape contains three files A B and C File A occupies a single partition 0 File B occupies three partitions that are linked consecutively 1 2 3 File C occupies eight nonconsecutively linked partitions 4 13 14 15 16 17 18 19 indicating that partitions 5 6 7 8 9 10 11 12 were not writable at the time file C was written to the tape TTAs 5 6 7 8 9 10 11 12 Figure 1 Example Tape Tiering Accelerator partition allocation The command procedures and their command formats are summarized below Set Host Type Command X 77 20 byte parameter data Use the PSF set host to identify the drive as a StorageTek drive The following parameter data byte must be set e Byte 0 X40 e Byte 2 X 08 The set host type command must be issued befor
21. into BOT because partition 1 is no longer backward linked to partition 2 Tape Tiering Accelerator Layout A StorageTek T10000C tape drive formatted for Tape Tiering Accelerator is represented in the StorageTek T10000C tape drive format specification It has five sections of 96 partition instances for a total of 480 partition instances The partition instances are organized in a linear serpentine pattern starting at ALP 1 at the beginning of tape BOT at the bottom left side increasing sequentially down the length of tape to end of tape EOT on the right side and then returning to BOT Figure 8 shows this pattern Tape Tiering Accelerator Capacity For the StorageTek T10000C tape drive each partition is approximately 9 GB 480 9 GB is not equal to the full 5 000 GB that can fit on a StorageTek T10000C tape drive This loss of full capacity is needed to allow the partition instances to be written in any order Potential Tape Tiering Accelerator Benefits and Effects Increased Access Times If an application identifies data for frequent access that data can be located in partition instances at the beginning of the tape for fast access The host can control where data is located on tape by setting writable partition instances Like data sets can be located together so that access to multiple files of like data can be performed more efficiently Efficient Use of Tape Capacity Depending on the application much of the data on a parti
22. ive does not allow the next partition to wrap around the writable list For example partition 255 will not be forward linked to partition 20 The drive will report LEOV on the last free partition in a manner similar to a normal tape The amount of space between LEOV and PEOV has not changed When starting a write the drive uses the current block as the append point just like in normal tape operation with one exception if the write command is proceeded by a start new logical volume the drive writes at block 0 at the start of the current partition The host should be located at the start of the partition before the Start New Logical Volume command is issued Regardless of where the host is logically positioned the write will take place at the start of the partition When the application is finished writing a file the application should issue a Detect Current TTA State command sequence and the partition number where the last block was written will be in bytes 16 and 17 Reading When treading the tape the drive automatically moves to partition instances that are linked together For example if the host is positioned to read partition 11 the drive transitions from partoition 4 to 5 10 and 11 with no host intervention It is assumed that the host does not read old host files as a matter of course But if the host requests to read the start of host file B in partition 2 for example the data is returned until the end of partition 2 at whi
23. nd 16 files S and T Partial Logical Volume A partial logical volume is a Tape Tiering Accelerator group in which instances are linked together with either no block 0 or no physical EOD or neither a block 0 or an EOD In Figure 9 there are five partial logical volumes Partitions 0 and 1 are a partial logical volume with a block 0 but no physical EOD Partitions numbers 16 17 18 and 19 make up a partial volume with no block 0 but it does contain an EOD Partition 5 partition 8 and partition numbers 11 12 and 13 are partial volumes without a block 0 or a physical EOD These partial logical volumes contain the files that were not 11 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator expired for the originally written logical volume shown in Figure 3 When combined they still represent that logical volume Writing When writing the drive only allows writes on partition instances identified with the Set Writable TTAs command using the Map TTA Partition command sequence On load the tape defaults to no partition instances being writable The host should give the Set Writable TTAs command by using the Map TTA Partitions command mask after load and this must be done at BOT If the Set Writable TTAs command isn t issued the tape will operate in a read only mode The drive always chooses the lowest partition after the current partition when linking multiple instances of partitions The dr
24. order X 67 4 byte parameter data to convert to standard tape This command sequence will convert a Tape Tiering Accelerator formatted tape back to a standard formatted tape however this process is not recommended except in situations where a standard tape was accidently formatted as a Tape Tiering Accelerator tape and never used The process of How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator positioning and processing Tape Tiering Accelerator formatted tapes may cause wear and debris to form around partition start and could degrade the tape s performance as a standard format tape Perform subsystem function PSF suborder x 67 is used to remove the partitions and revert to standard format The parameter data format is as follows 1 PSF command with parm bytes 0 3 equal to X 67000000 reverts to standard format 2 Write at least one block and nonbuffered sync or one nonbuffered tape mark Any number of blocks can be written such as labels followed by a nonbuffered tape mark Tape Tiering Accelerator Examples These examples demonstrate typical uses for Tape Tiering Acclerator to save space and improve access time Save Space To format a Tape Tiering Accelerator tape the application issues a set TTA mode command The tape should be empty or it should be a scratch tape since initializing it may prevent access to data previously written on the tape Formatting a Tape Tie
25. r capable Map Tape Tiering Accelerator Partitions Command X 77 suborder X66 132 byte parameter data to enable partitions for write Perform subsystem function PSF suborder x 66 is used to define the partition map which will enable individual partitions for read only or write authority The map size is 128 bytes with a 4 byte header for a total parameter length of 132 bytes The parameter data format is as follows e Bytes 0 3 X 66008000 e Bytes 4 126 Partition authorization bits The StorageTek T10000C tape drive supports 480 partitions represented as 0 479 Each bit position starting with the high order bit of byte 4 through the low order bit of byte 64 represents the corresponding partition number s state A B 1 represents write authorization and a B 0 represents read only authorization The remaining bits are reserved for future use setting those bits to B 1 will result in a command reject status parameter exception For example X 6600800080 Partition 1 is enabled for write the remaining bytes are set to zero X 66008000C0 Partitions 1 and 2 are enabled for write the remaining bytes ate set to zero X 66008000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFPF Every partition is enabled for write the remaining bytes must be set to zero otherwise command reject status is returned X 66008000
26. ring Accelerator tape divides the tape into a fixed number of empty partitions with a guard band allocated between each partition Next the application sets a write mask by issuing a map TTA partitions command this command tells the tape drive which instances of partitions to link together during subsequent write operations In Figure 2 the first 20 instances of partitions on tape have been mapped for writing Each block is an empty partition that can be used by the application Files Empty No data has been written to the tape ALPs Figure 2 An empty Tape Tiering Accelerator tape The application now sends a locate TTA command to partition number 1 and a start new logical volume command sequence The application now can begin writing to this logical volume on tape using standard tape write commands This process may occur over multiple mount and dismount cycles and across several drives In Figure 3 below the application writes nine files Those files span all 20 instances of partition The data shown in the top row are application files and the bottom row indicates the physical relationship of the 20 instances of partitions to those files The files can span one or more instances of partitions or be contained within a single partition Files ALPs Figure 3 Host files and Tape Tiering Accelerator allocation How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator Over time the fil
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28. sing Tape Tiering Accelerator April 2014 Oracle Corporation World Headquarters 500 Oracle Parkway Redwood Shores CA 94065 U S A Worldwide Inquiries Phone 1 650 506 7000 Fax 1 650 506 7200 oracle com as Oracle is committed to developing practices and products that help protect the environment Copyright 2014 Oracle and or its affiliates All rights reserved This document is provided for information purposes only and the contents hereof are subject to change without notice This document is not warranted to be error free nor subject to any other warranties or conditions whether expressed orally or implied in law including implied warranties and conditions of merchantability or fitness for a particular purpose We specifically disclaim any liability with respect to this document and no contractual obligations are formed either directly or indirectly by this document This document may not be reproduced or transmitted in any form or by any means electronic or mechanical for any purpose without our prior written permission Oracle and Java are registered trademarks of Oracle and or its affiliates Other names may be trademarks of their respective owners Intel and Intel Xeon are trademarks or registered trademarks of Intel Corporation All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International Inc AMD Opteron the AMD logo and the AMD Opteron logo are trademark
29. structure These values are used later when the new host file is accessed or for determining when a partition is free to be reused Next the host writes the new file Another detect current TTA state command sequence is issued to determine the current partition Based on the starting partition and current partition the host can determine in which partition instances the file resides This information is kept in the host file location structure and later used to determine when a partition is free to reuse Writing a Host File to a Free Tape Tiering Accelerator When users start a new logical volume the first command to issue is a locate TTA command to the first free partition that is kept by the host file location structure Next the host file location structure is 15 How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator updated with the first free partition and a host block ID of 0 Next the host initiates a start new logical volume command sequence and writes the new file A detect current TTA state command sequence is issued to determine the current partition Based on the starting partition and current partition the host can determine in which ALPs the file resides This information is kept in the host file location structure and later used to determine when a partition is free to reuse Tape Tiering Accelerator Data Definitions RSSD data definition MACRO RSSDMAP KKKKKKKKKKKKKKKKKKKKKKKKK
30. tition 5 and E and N end of partition 8 are wasted space This space is not empty it contains the residual data from the expired files B and F If the application attempts to read the old file B data the beginning of that file will be read Then the drive will report an end of data EOD error at the end of ALP 1 As a result the application will need to stop reading at the end of file A This process is discussed in detail below Files ALPs Figure 5 New files written to freed partitions The application has to retain a record of the start of each record host block ID and ALP number to navigate through logical volumes where files have expired and partitions are reallocated to a new logical volume To enable the first logical volume yellow in Figure 5 to be read the the following steps must be taken 1 Locate to TTA 0 2 Locate to the start block ID for record A 3 Read record A How to Capture Wasted Cartridge Space in z OS Implementations Using Tape Tiering Accelerator 4 Locate to TTA 5 5 Locate to the start block ID for record C 6 Read records C D and E 7 Locate to TTA 11 8 Locate to the start block ID for record G 9 Read records G H and I Users should note that it is necessary for the application to track which set writeable TTA command map corresponds to each logical volume There is a different write map for the first yellow and second green logical volumes Now the assumption is that

How to Capture Wasted Cartridge Space in z/OS

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