Month: February 2012

How to Add/Drop Disk in ASM

Its not that quite often your SA asks you to release one of the disks that you been using it for a while for your database but if they do then you need to know how to remove the disk and add a new disk from your ASM.
Here are the steps to Add and Drop a Disk from ASM Diskgroup. Note that asm_power_limit parameter once set is permanent as it writes to both spfile as well (check alert log when you do alter session set asm_power_limit = 10 command to see that it converts it into scope=both).
What’s asm_power_limit parameter? 
In simple words, Think that you are increasing the work force to finish the job (re-balancing the disk(s)) quicker. You can read more in Oracle Docs.
OK, Coming to simple steps to Add a Disk:
  1. Assign the disk to ORACLEASM
    1. /etc/init.d/oracleasm createdisk TIER2_DATA03 /dev/mapper/mpath14p1
  2. ScanDisk in ALL NODES
    1. /etc/init.d/oracleasm scandisks
  3. Check the header_status in v$asm_disks to make sure that the disk can be added (check below for each status description)
    1. Login as sqlplus / as sysasm – note SYSASM here… (for 11g)
    2. set lines 200
    3. select group_number, substr(path,1,20) path, substr(name,1,20) disk_name, total_mb, free_mb, state, header_status, mode_status from v$asm_disk;
  4. Now Add the Disk to diskgroup.
    1. alter diskgroup TIER2_DATA add disk ‘ORCL:TIER2_DATA03’; –At this point the new disk is added to the group and Re-Balancing is occurring in the background (basically spreading the data across all the disks along with the new one in that diskgroup)
  5. Check the status in v$asm_operations for rebalancing action.
    1. select * from v$asm_operation;
  6. You are ready to start using the new disk.
  7. Drop the old Disk
    1. alter diskgroup TIER2_DATA drop disk TIER2_DATA01; –At this point, all the data on disk that you are dropping is being distributed to other disks within that diskgroup.
    2. select *from v$asm_operation; –to check the status on rebalancing while dropping the disk
  8. Once dropped from ASM, delete from oracleasm library:
    1. [root@ndhdbd1 disks]# /etc/init.d/oracleasm deletedisk TIER2_DATA01
  9. Removing ASM disk “TIER2_DATA01”:                          [  OK  ]
  10. ScanDisk in ALL NODES
    1. /etc/init.d/oracleasm scandisks

V$ASM_DISK Header_Status Info:

  • UNKNOWN – Automatic Storage Management disk header has not been read
  • CANDIDATE – Disk is not part of a disk group and may be added to a disk group with the ALTER DISKGROUP statement
  • INCOMPATIBLE – Version number in the disk header is not compatible with the Automatic Storage Management software version.
  • PROVISIONED – Disk is not part of a disk group and may be added to a disk group with the ALTER DISKGROUP statement. The PROVISIONED header status is different from the CANDIDATE header status in that PROVISIONED implies that an additional platform-specific action has been taken by an administrator to make the disk available for Automatic Storage Management.
  • MEMBER – Disk is a member of an existing disk group. No attempt should be made to add the disk to a different disk group. The ALTER DISKGROUP statement will reject such an addition unless overridden with the FORCE option
  • FORMER – Disk was once part of a disk group but has been dropped cleanly from the group. It may be added to a new disk group with the ALTER DISKGROUP statement.
  • CONFLICT – Automatic Storage Management disk was not mounted due to a conflict
  • FOREIGN – Disk contains data created by an Oracle product other than ASM. This includes datafiles, logfiles, and OCR disks.

Don’t be a Crash Test Dummy

During a recent Oracle 11g Tuning Course in London, a discussion of performance problems related to locking and resource serialisation arose during the lessons dealing with contention. I was then asked by a student to summarise the types of serialisation that occur and to describe the worst types that I find at customers. I replied […]

Scheduling Options in Primavera P6 by David Kelly

These options are made available by choosing the Options button, from the scheduling dialogue.

In a properly configured P6 environment, where projects are created by copy/paste from an official template created by the central project controls group, these settings will be correct.

Ignore relationships to and from other projects

In almost all circumstances the default, not to ignore such relationships, would be correct. An example of where this toggle switch is valuable is if all scope variations were held in a separate project. With both projects open, scheduling shows the combined projects. With just the original project open and this option switched on, the original scope only is scheduled. This is one of thimge simplest ways to switch between original scope and current scope.

Make open ended activities critical

This is a not just a display option, it changes the float on any path with an open end.

Use Expected Finish dates

Expected Finish is a controversial way to report progress. Effectively, rather than telling a P6 activity how much work has been done by reporting a per cent complete and allowing P6 to calculate when we can expect the activity to finish, we input an expected finish date and P6 calculates how much work has been done. Many project controls professionals think this is the wrong way round. Even if such dates have been added in the Status tab of the Activity screen, they will not be used if this option is unchecked. The arithmetic is NOT commutative. It will NOT put the original values back if you un-check this. Be careful!

Schedule automatically when a change affects dates

Switching “real-time” scheduling on such that the schedule recalculates with every significant change to the data is not advised. This feature is the preserve of light-weight single-user planning systems.

Level Resources During Scheduling

This is largely a matter of style. Some planners prefer to see the results of the schedule before resource levelling, others having satisfactorily set the levelling parameters would rather both processes were run together.

Recalculate assignment costs after scheduling

It is hard to imagine a scenario where one would NOT want to recalculate an activity’s costs based on the new dates that the activity may have once scheduled.

Retained Logic vs. Progress Override

None of the above settings creates as much discussion as this one. The controversy arises when there is out-of-sequence progress.

The above Barchart shows two projects which are identical in every respect except for that setting. The only progress that has been achieved is that the site has been prepared. Using Progress Override means that the remaining duration of the activity “Prep site and Erect” starts at the data date. This is clearly nonsense. Note that the whole project now finishes earlier than the Retained Logic project which leaves the remaining duration in the position that its predecessors demand. What is going on here, why do these options exist?

In the real world most planners add relationships to a project for two reasons:

  1. The laws of physics. If you are going to put a pipe in a trench, you must make the trench first.
  2. Not enough resource information. If I need to machine two valve blocks, and I do not know all or any of:
  • Exactly how much machine time and labour time is required for each of them.
  • My resource dictionary does not properly describe the availability of the equipment and labour to do the job,
  • I do not have clear guidance from management about the priority for allocation of resources
  • BUT, I “know” I can only do one at a time – Then I add a finish to start relationship between the two activities.
  • In case 2) above it does not matter if we start the successor activity first, and is we did start it first we would need to finish it before starting on the predecessor. In a perfect world case 2) above is easily dealt with by resource levelling, but quite a lot more information is required to do it the correct way.

    Calculate start to start lag from

    Clearly Actual Start may calculate more realistic dates. Probably Early Start calculates more optimistic dates if the schedule is slipping.

    Define Critical Activities as

    The definition of Critical in textbooks of CPM methodology is where float is less than or equal to zero. The longest path through the network always shows red bars in the barchart for the so-called Critical path, and is a more popular choice.

    Calculate Float based on Finish date of

    When scheduling multiple projects – perhaps a portfolio that represents a single contract – how many float paths? Does each project have its “own” float, or is float “owned” by the whole portfolio of projects? Before considering this question we would need to know how the projects’ inter-project relationships are structured, how many open ends there are in how many of the projects, and an understanding of the commercial/contractual implications. It is unlikely that the planner on the project can answer this question alone.

    Compute Total Float as

    The author admits defeat here. Apparently in some circumstances an LoE or WBS Summary activity can have different Start and Finish Floats. There is no Primavera documentation that describes the circumstances or justifies the arithmetic. Choose Finish Float.

    Calendar for calculating relationship lag

    This is very important. Best practice is to always use 24hour, and always enter lags in hours. E.g. if the lag is 5 days, enter 120h into the lag dialogue. This way no changes in any calendar will change the wall-clock time of any lag

    NOTE: When you schedule in P6 all open projects are scheduled at the data date selected for each project. If only one project is open, then you can change the data date for that project. If multiple projects are open then you can only change their data date in the Projects screen, where you can even “Fill Down” a new data date to multiple projects.

    About the Author:

    David Kelly

    Dave Kelly delivers Oracle Primavera training courses at Milestone in Aberdeen; Milestone is an Oracle University Authorised Education Centre and offers the complete Oracle Primavera course curriculum. Dave has been involved in Planning and Scheduling software training and consultancy for many years he is well known and respected as an expert in delivering Primavera and associated solutions as both an experienced consultant and trainer.

DST in Russia

Daylight Saving Time in Russia has been changed last year. Oracle published a FAQ on the support site about this: Russia abandons DST in 2011 – Impact on Oracle RDBMS [ID 1335999.1]. In short if you are using DATEs and TIMESTAMPs without time zone in your application, you are almost “safe” and there’s most likely […]

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