1 / 11

Figure 25.1 Organization of memory.

Figure 25.1 Organization of memory. Figure 25.2 Log example. Figure 25.3 The recovery procedure can handle database restoration correctly with a write-ahead log.

shea-leon
Download Presentation

Figure 25.1 Organization of memory.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Figure 25.1Organization of memory.

  2. Figure 25.2Log example.

  3. Figure 25.3The recovery procedure can handle database restoration correctly with a write-ahead log.

  4. Figure 25.4Implementing durability using a force policy. It might be necessary to force the pages a transaction has updated out of the cache before the transaction’s commit record is written to the log. Before the dirty page updated by T, containing LSN value j, can be written to the database, it might be necessary to force the log buffer (1) so that the update record with LSN equal to j is on mass storage. After the dirty page has been written (2), the commit record for T can be appended to the log buffer (3). The log buffer can be written to the log at some later time.

  5. Figure 25.5Implementing durability using an after-image with a no-force policy. The write-ahead feature requires that, before a dirty page updated by T can be written to the database (2), the corresponding update record must be written to the log on mass storage (1). Although the commit record cannot be written before the update record, the relationship between the time the commit record is written and the time the dirty page is written is not constrained.

  6. Figure 25.6Log showing records for an aborted transaction that has updated database variable x. The log contains both an update record and a compensation log record for x.

  7. Figure 25.7Use of fuzzy checkpoints.

  8. Figure 25.8(a)Effect of transactions being active while a dump is taken.

  9. Figure 25.8(b)Effect of transactions being active while a dump is taken (continued).

  10. Figure 25.8(c)Effect of transactions being active while a dump is taken (continued).

More Related