Navigating the Logging environment panel

Use the following procedure to view and model the logging environment.

Related topic

Using-the-PACLOG-logging-environment-modeling-tool

To view and model the logging environment

  1. In the PACLOG main menu panel, select 1. Logging environment - Display and/or model changes to DB2* logging.

  2. In the Subsystem ID field, enter a subsystem ID and press Enter.The Logging Environment panel is displayed.

    ALMLG00A ============== Logging Environment  ===========================
    Command ===> __________________________________________________________________
                                                                                  
                                                                                  
    Type information. Then press Enter.                                           
                                                                                  
       Option . . . 1 1. Model       Display current statistics & model changes    
                      2. Actives     Display active log information                
                      3. Archives    Display archive log information               
                                                                                  
       DASD type. . 2 1. 3380        Device type used in rate calculations         
                      2. 3390

  3. For Option, enter 1. Model, specify the DASD type in your environment, and press Enter:
    The Logging Environment Model for SSID panel is displayed.

    ALMLG01A ========== Logging Environment Model for ABCD  =======================
    Command ===> __________________________________________________________________
                                                                                  
    Type information and press Enter.                                              
      Source of highest logging rate **  . . . . . . 1 1. BSDS  2. User  3. List   
      Optimize fields marked * for DASD archives . . 1 1. Yes   2. No              
                                                                                  
       Current                                      Model     Prev                 
               Expected compression ratio . . . . . __            0-95           
            61 Days of log data recorded in BSDS. . ___            1-366          
          0.00 Hours of log required on DASD. . . . ___            1-999          
        742500 High logging rate for that period. . _____ **       1-99999        
           550 Active log size (cylinders each) . . _____  *       1-99999        
             3 Number of active log pairs . . . . . __     *       3-93           
         10000 Number of entries in BSDS  . . . . . _____  *       1-10000        
    assuming 0 Hours of archive 2 on DASD . . . . . ___    *       0-999  (0=tape)
    assuming 0 Hours of archive 1 on DASD                                          
          3300 Total cylinders without PACLOG                                      
               Total cylinders with PACLOG                                         
               Cylinders saved by PACLOG

    You can use the Logging Environment Model panel to change the following logging environment variables to see what effect those changes would have on the required amount of DASD and other logging environment variables:

    • Days of log data recorded in the BSDS
    • Hours of log required on DASD
    • Highest logging rate
    • Active log size in cylinders
    • Number of active log pairs
    • Number of entries in the BSDS
    • Hours of archive 2 on DASD

    In addition, you can choose to have the modeling tool optimize your logging environment based on these criteria:

    • The number of days of log data that you want to record in the BSDS
    • The number of hours of log that you require to be kept on DASD

Logging environment panel field descriptions

The following table describes the fields on the Logging Environment Model panel:

Field

Description

Source of highest logging rate

Determines how the logging environment model obtains the highest logging rate: from the BSDS, a user entry, or a list of previous rates

  • Select BSDS to display the highest logging rate found in the BSDS. The logging environment modeling tool searches the BSDS to find the highest rate of activity for the period of nn hours, where nn equals the value in the Hours of log required on DASD field.
  • Select User if you want to enter the highest logging rate yourself in the High logging rate for that period field.
  • Select List to select the highest logging rate from a list encompassing the highest rates of activity for the period of nn hours, where nn is the number of hours for which the average logging rate is calculated. Use the Hours of log required on DASD field to specify nn. When the list is displayed, enter / or S beside the rate you want and press Enter.

Optimize fields marked * for DASD archives

The logging environment modeling tool can calculate the optimal size of your active logs, assuming that the archive logs will be on DASD. All fields marked with a * are included in the optimization process. To perform the optimization, select Yes in this field, enter data in the following fields, and then press Enter.

  • Hours of log required on DASD
  • Days of log data recorded in BSDS
  • Expected compression ratio

The tool initializes the following fields and then performs the optimization.

  • Number of active log pairs is set to 3
  • Number of entries in BSDS is set to 1000
  • Hours of archive 2 on DASD is set to 1

Current

Figures in the Current column describe the current logging environment of your system as determined from the BSDS.

Model

Fields in the Model column allow you to change the logging environment settings in order to determine the overall effect of the changes on DASD or the logs.

Prev

The Prev column displays the results of the previous model you created, allowing you to compare two different scenarios.

Expected compression ratio

Displays expected compression of an archive log when PACLOG is used. Compression percentages of 70 to 90 percent can be expected in most circumstances.

Days of log data recorded in BSDS

Displays the number of days of log data to be kept in the BSDS. We recommend that you keep a few more days than is usually necessary to allow for periods of unexpectedly high activity. For example, if you want 14 days of log available for recovery, then you should ensure that you have 17 days of log available in the BSDS.

If you select Yes in the Optimize fields marked * for DASD archives field, then you must enter the number of days you want to keep log data.

If you select No in the Optimize fields marked * for DASD archives field, then this value is calculated as follows:

(active log size) × (number of entries in BSDS) / (highest logging rate) × 24

Hours of log required on DASD

Displays the number of hours you want to retain log data on DASD. This is the length of time that you want recovery data to be available on DASD. Valid values range from 1 to 999.

If you do not archive to DASD (hours of archive 2 on DASD=0), then the value entered in this field, along with the average logging rate for this time period, is used to determine the number of days of data that is stored in the BSDS.

Important

The value in the Current column is the value determined by the shortest length of time taken to fill all of the active log data sets.

High logging rate for that period

The logging environment modeling tool searches the BSDS to find the highest rate of log activity for the period of nn hours, where nn equals the value in the Hours of log required on DASD field.

You can also enter a logging rate manually or choose a logging rate from a list of high rates.

  • To have the logging environment modeling tool find the highest rate, select BSDS in the Source of highest logging rate field.

  • To enter the logging rate of your choice, select User in the Source of highest logging rate field and enter the logging rate you want in this field.

    Valid values range from 1 to 99999 cylinders per hour.

  • To select a logging rate from a list of the highest 15 logging rates, select List as the Source of the highest logging rate and press Enter. When the list is displayed, enter S or / beside your choice and press Enter.

Active log size

Displays the active log size in cylinders

If you select Yes in the Optimize fields marked * for DASD archives field, then the size in cylinders is calculated as follows:

A × 24 × B / C + 1

Variable

Equals

A

Number of days of data in BSDS

B

High logging rate

C

Number of entries in the BSDS

If you select No in the Optimize fields marked * for DASD archives field, then you must enter a value for the active log size.

Number of active log pairs

Displays the number of active log pairs for the Db2 subsystem. The entry in the Current column shows your current Db2 log configuration.

We recommend that you keep only three active logs if you place archive logs on DASD. In the event of a DASD failure on any log, Db2 operation can continue unimpeded with the two remaining logs while you recover the third log. Keeping only three logs also reduces redundant log information (the active data that is replicated in the archive log data sets). 

If you select Yes in the Optimize fields marked * for DASD archives field, then the logging environment modeling tool sets the number of active log pairs to 3.

Number of entries in BSDS

Displays the number of entries kept in the BSDS. The entry in the Current column shows the number of entries currently kept in the BSDS. We recommend that you always use the maximum value of 1000. The amount of DASD space occupied by these entries is only a few cylinders. If you select Yes in the Optimize fields marked * for DASD archives field, the logging environment modeling tool sets this figure to 1000.

If you do not currently keep 1000 entries in the BSDS, you can determine how changing the number of entries affects the number of days of log data recorded in the BSDS by performing log environment modeling.

Hours of archive 2 on DAS

Displays the amount of time that you want to retain ARCHLOG2 on DASD before migrating it to tape. The logging environment modeling tool sets this to one hour when you choose to optimize. You can also use the logging environment modeling tool to determine the impact on DASD usage if you are currently keeping more than the optimal number of hours. To view the effect of keeping a larger number of hours of ARCHLOG2 on DASD, follow these steps:

  1. In the Optimize fields marked * for DASD archives field, select No.
  2. Set or verify the following fields:
    • Expected compression ratio
    • Days of log data recorded in BSDS
    • Hours of log required on DASD
  3. Set the Hours of archive 2 on DASD as desired, and then press Enter.

Important

If you do not store either copy of the archive log on DASD, set this value to 0.

Hours of archive 1 on DASD

Displays the amount of time that ARCHLOG1 should be retained on DASD before migrating it to tape. This figure is determined by the number of hours you indicate in the Hours of log required on DASD field.

Total cylinders without PACLOG

Displays the total number of cylinders required if you do not use PACLOG compression which is calculated in the following formulas.

  • If you do not keep any archive log on DASD (hours of archive 2 on DASD=0), the total number of cylinders required is as follows:

    A × B × 2 (if you are using dual logs)

  • If you keep archive data on DASD, the total number of cylinders required is as follows:

    (A × B × 2) + (C × [D - E]) + (C × F)

Variable

Equals

A

Size of the active log data sets

B

Number of log data sets

C

Highest logging rate

D

Number of hours of ARCLOG1

E

Total hours of active log

F

Hours of ARCLOG2

Total cylinders with PACLOG

Displays the total number of cylinders required if you use PACLOG compression that is calculated as the amount required without PACLOG, except that the requirements for ARCLOG1 and ARCLOG2 are reduced by the percentage you entered in the Expected compression ratio field.

Cylinders saved by PACLOG

Displays the number of cylinders saved by using PACLOG compression that is calculated by subtracting the cylinders required when using PACLOG from the cylinders required when not using PACLOG.

 

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