Seagate ST43401N/ND Guide d'installation télécharger pdf (Page 70)

If Your Version is 11.5

This section covers the following topics:

• New Rollback Records

• Optimizer Changes

• Trace Flag 326

New Rollback Records

New rollback records added to the transaction log in 11.9.2 may require you to

add more space to the

syslogs system table. Rollback records are logged

whenever a transaction is rolled back. For every update record that is rolled

back, a rollback record is logged.

To make sure that there is always space for rollback records in the event of a

rollback, ASE saves enough space to log a rollback record for every update

belonging to an open transaction. If a transaction completes successfully, no

rollback records are logged and the space reserved for them is released.

To calculate the increased amount of space that needs to be added to the

transaction log to accommodate rollback records, you need to estimate:

• The number of update records in the transaction log that are likely to

belong to already rolled-back transactions.

• The maximum number of update records in the transaction log that are

likely to belong to open transactions at any one time.

Each rollback record requires approximately 60 bytes of space, or 3 one

hundredths of a 2K page. Thus, the calculation for including rollback records

(RRs) in the transaction log is:

(logged RRs + # open updates) * 3/100

In addition to increasing the size of the transaction log to handle rollback

records, it may also be useful to add log space to compensate for the effects of

rollback records on the last-chance threshold (LCT) and on user-defined

thresholds.

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Seagate ST43401N/ND Guide d'installation Page 70