1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
Database validation allows to run low-level checks of consistency of on-disk
structures and even to fix some minor corruptions. It is recommended procedure
for any valuable database, i.e. DBA should validate database from time to time
to make sure it is healthy. But validation process requires exclusive access to
database, i.e. it forbids any kind of concurrent access to database while
validation runs. It could be a big problem to stop user access, especially when
database is large and validation takes notable amount of time.
Online validation is a new feature which allows to perform some consistency
checks without exclusive access to database. Online validation allows to:
- validate some (or all) user tables in database
- validate some (or all) indices
- system tables are not validated
- other ODS checks (such as Header\PIP\TIP\Generators pages) are not run by
online validation
- while table (and/or its index) is validated user attachments are allowed to
read this table. Attempt to INSERT\UPDATE\DELETE will wait until validation
finished or will return lock timeout error (depends on lock timeout of user
transaction)
- while table (and/or its index) is validated any kind of garbage collection at
this table is disabled - background and cooperative garbage collection will
just skip this table, sweep will be terminated with error.
When online validation starts to check table it makes few actions to prevent
concurrent modifications of table's data:
- acquires relation lock in PR (protected read) mode
- acquires (new) garbage collection lock in PW (protected write) mode.
Both locks are acquired using user-specified lock timeout. If any lock request
fails error is reported and table is skipped.
Then table and its indices are validated in the same way as full validation does.
Then locks are released and next table is validated.
Online validation is implemented as Firebird service and accessible via Services
API. Therefore gfix utility can't run online validation. fbsvcmgr utility has
full support for new service, syntax is:
fbsvcmgr [host:]service_mgr [user <...>] [password <...>]
action_validate dbname <filename>
[val_tab_incl <pattern>]
[val_tab_excl <pattern>]
[val_idx_incl <pattern>]
[val_idx_excl <pattern>]
[val_lock_timeout <number>]
where
val_tab_incl pattern for tables names to include in validation run
val_tab_excl pattern for tables names to exclude from validation run
val_idx_incl pattern for indices names to include in validation run,
by default %, i.e. all indices
val_idx_excl pattern for indices names to exclude from validation run
val_lock_timeout lock timeout, used to acquire locks for table to validate,
in seconds, default is 10 sec
0 is no-wait
-1 is infinite wait
Patterns are regular expressions, they are processed by the same rules as
"SIMILAR TO" expressions. All patterns are case-sensitive (despite of database
dialect!).
If pattern for tables is omitted then all user tables will be validated.
If pattern for indices is omitted then all indices of tables to validate will
be validated.
System tables are not validated.
Examples:
1. fbsvcmgr.exe service_mgr user SYSDBA password masterkey
action_validate dbname c:\db.fdb
val_tab_incl A%
val_idx_excl %
val_lock_timeout 0
this command will validate all tables in database "c:\db.fdb" with names
starting with "A". Indices are not validated. Lock wait is not performed.
2. fbsvcmgr.exe service_mgr user SYSDBA password masterkey
action_validate dbname c:\db.fdb
val_tab_incl "TAB1|TAB2"
this command will validate tables TAB1 and TAB2 and all their indices.
Lock wait timeout is 10 sec.
Note, to specify list of tables/indices it is necessary to:
a) separate names by character "|"
b) don't use spaces : TAB1 | TAB2 is wrong
c) whole list should be enclosed in double quotes to not confuse command
interpreter
Vlad Khorsun, <hvlad at users sourceforge net>
|
