3.3 Operational considerations

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The following are items to consider when you are using TVS:

3.3.1 Can I stop/start the use of Logger?

System Logger provides a critical function within Transactional VSAM, and Transactional VSAM cannot operate without the services of the System Logger. If System Logger is not available when Transactional VSAM initializes, it does not complete initialization and waits for System Logger to become available. Unfortunately, there is no message issued to indicate that Transactional VSAM is waiting for System Logger.

If System Logger should fail after Transactional VSAM initializes, Transactional VSAM does not detect the loss of System Logger until the next request for Transactional VSAM services comes from a batch job. At that point, Transactional VSAM issues the following error messages:

Example 3-12: Messages from DFSMStvs when it detects System Logger is gone

 IGW839I 05012003 08.15.09 AN ERROR OCCURRED DURING SYSTEM LOGGER OPERATION IXGWRITE FOR SYSTEM LOG STREAM IGWTV002.IGWLOG.SYSLOG. SYSTEM LOGGER RETURN CODE 00000008 REASON CODE 00000890 IGW827I 05012003 08.15.09 A FAILURE HAS OCCURRED WHILE WRITING TO THE SYSTEM LOG IGWTV002.IGWLOG.SYSLOG . ACCESS TO THE SYSTEM LOG HAS BEEN LOST. TRANSACTIONAL VSAM WILL BE TERMINATED. IGW471I DFSMS VSAM RLS  REQUEST TO DISABLE TRANSACTIONAL VSAM  INSTANCE  IGWTV002 IS ACCEPTED. DISABLE REASON: TRANACTIONAL VSAM DETECTED SYSTEM LOGGER ENVIRONMENTAL ERROR

After this, Transactional VSAM is unavailable.

3.3.2 Defining log streams dynamically

Unlike CICS TS, Transactional VSAM does not support log stream models; every log stream that Transactional VSAM needs must be defined in the System Logger policy BEFORE Transactional VSAM attempts to use it. How Transactional VSAM reacts to a missing log stream depends on which log stream is not defined in the LOGR inventory:

Undefined log stream	How Transactional VSAM reacts
Undo log stream	Transactional VSAM does not initialize
forward recovery log stream	Transactional VSAM fails the open of the data set
log-of-logs	Transactional VSAM continues processing without it

3.3.3 Displaying log stream information

In addition to the System Logger DISPLAY LOGGER command (refer to "Display Logger command" on page 244), Transactional VSAM displays log stream information in response to several commands. The D SMS,TRANVSAM command displays information about Transactional VSAM in general, including log stream information. Here is an example of the command response:

Example 3-13: Output from D SMS,TRANSVSAM command

 IEE932I 033 IGW800I 08.42.44 DISPLAY SMS,TRANSACTIONAL VSAM DISPLAY SMS,TRANSACTIONAL VSAM - SERVER STATUS  System   TVSNAME  State   Rrs    #Urs     Start     AKP    QtimeOut  -------- -------- ------ ----- -------- --------- -------- --------  #@$2     IGWTV002 ACTIVE REG          0 WARM/WARM     5000      300 DISPLAY SMS,TRANSACTIONAL VSAM - LOGSTREAM STATUS  LogStreamName              State      Type       Connect Status  -------------------------- ---------- ---------- --------------  IGWTV002.IGWLOG.SYSLOG     Enabled    UnDoLog    Connected  IGWTV002.IGWSHUNT.SHUNTLOG Enabled    ShuntLog   Connected  #@$C.CICSVR.LGOFLOGS       Enabled    LogOfLogs  Connected  #@$#.CICSVR.F01DACCT       Enabled    FrLog      DisConnected

You can also get more detailed information about a single log stream (or all log streams) using the D SMS,LOG command. You can either specify the name of a specific log stream or use the keyword ALL, which results in information for ALL log streams known to all instances of Transactional VSAM within the sysplex. Here is the output from the display request against a single log stream using D SMS,LOG(IGWTV002.IGWLOG.SYSLOG):

Example 3-14: Output from D SMS,LOG(IGWTV002.IGWLOG.SYSLOG) command

 IGW804I 08.51.32 DISPLAY SMS,LOG DISPLAY SMS,LOG      - LOG STREAM STATUS   Name: IGWTV002.IGWLOG.SYSLOG     State: Enabled      Type: UnDo   System   TVSNAME  JobName  Urid of Oldest Log Block   -------- -------- -------- --------------------------------   #@$2     IGWTV002 TVSV07C  B95AAE067E743374000005FD01030000* DISPLAY SMS,LOG      - LOG STREAM USAGE   LogStreamName: IGWTV002.IGWLOG.SYSLOG   System   TVSNAME  JobName  JobName  JobName  JobName  JobName   -------- -------- -------- -------- -------- -------- --------   #@$2     IGWTV002 TVSV05C  TVSV07C  TVSV08C  TVS006C  TVS007C   #@$2     IGWTV002 TVS009C *OLDEST URID ACROSS ALL SYSTEMS IN THE SYSPLEX

Since Transactional VSAM cannot delete any log blocks that contain data associated with the oldest unit of recovery, you can use this command to determine which UR from which batch job is preventing Transactional VSAM from pruning the tail of the undo log stream.

3.3.4 Monitoring for offload conditions

The only way to monitor how many offload events occur within a given interval is to gather the SMF 88 records and use either the sample program IXGRPT1 or IXGRPT1J to format the data.

Unfortunately, short of taking a dump of the IXGLOGR address space, there is no way to determine how long a given offload event takes to complete.

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