diff options
Diffstat (limited to 'db2/log/log_findckp.c')
| -rw-r--r-- | db2/log/log_findckp.c | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/db2/log/log_findckp.c b/db2/log/log_findckp.c new file mode 100644 index 0000000000..67fe9c9f50 --- /dev/null +++ b/db2/log/log_findckp.c @@ -0,0 +1,130 @@ +/*- + * See the file LICENSE for redistribution information. + * + * Copyright (c) 1996, 1997 + * Sleepycat Software. All rights reserved. + */ + +#include "config.h" + +#ifndef lint +static const char sccsid[] = "@(#)log_findckp.c 10.10 (Sleepycat) 7/30/97"; +#endif /* not lint */ + +#ifndef NO_SYSTEM_INCLUDES +#include <sys/types.h> + +#include <errno.h> +#include <stdlib.h> +#include <string.h> +#endif + +#include "db_int.h" +#include "shqueue.h" +#include "log.h" +#include "txn.h" +#include "common_ext.h" + +/* + * __log_findckp -- + * + * Looks for the most recent checkpoint that occurs before the most recent + * checkpoint LSN. This is the point from which recovery can start and the + * point up to which archival/truncation can take place. Checkpoints in + * the log look like: + * + * ------------------------------------------------------------------- + * | ckp A, ckplsn 100 | .... record .... | ckp B, ckplsn 600 | ... + * ------------------------------------------------------------------- + * LSN 500 LSN 1000 + * + * If we read what log returns from using the DB_CKP parameter to logput, + * we'll get the record at LSN 1000. The checkpoint LSN there is 600. + * Now we have to scan backwards looking for a checkpoint before LSN 600. + * We find one at 500. This means that we can truncate the log before + * 500 or run recovery beginning at 500. + * + * Returns 0 if we find a checkpoint. + * Returns errno on error. + * Returns DB_NOTFOUND if we could not find a suitable start point and + * we should start from the beginning. + * + * PUBLIC: int __log_findckp __P((DB_LOG *, DB_LSN *)); + */ +int +__log_findckp(lp, lsnp) + DB_LOG *lp; + DB_LSN *lsnp; +{ + DBT data; + DB_LSN ckp_lsn, last_ckp, next_lsn; + __txn_ckp_args *ckp_args; + int ret, verbose; + + verbose = lp->dbenv != NULL && lp->dbenv->db_verbose != 0; + + /* + * Need to find the appropriate point from which to begin + * recovery. + */ + memset(&data, 0, sizeof(data)); + if (F_ISSET(lp, DB_AM_THREAD)) + F_SET(&data, DB_DBT_MALLOC); + if ((ret = log_get(lp, &last_ckp, &data, DB_CHECKPOINT)) != 0) + return (ret == ENOENT ? DB_NOTFOUND : ret); + ZERO_LSN(ckp_lsn); + + next_lsn = last_ckp; + do { + if (F_ISSET(lp, DB_AM_THREAD)) + free(data.data); + + if ((ret = log_get(lp, &next_lsn, &data, DB_SET)) != 0) + return (ret); + if ((ret = __txn_ckp_read(data.data, &ckp_args)) != 0) { + if (F_ISSET(lp, DB_AM_THREAD)) + free(data.data); + return (ret); + } + if (IS_ZERO_LSN(ckp_lsn)) + ckp_lsn = ckp_args->ckp_lsn; + if (verbose) { + __db_err(lp->dbenv, "Checkpoint at: [%lu][%lu]", + (u_long)last_ckp.file, (u_long)last_ckp.offset); + __db_err(lp->dbenv, "Checkpoint LSN: [%lu][%lu]", + (u_long)ckp_args->ckp_lsn.file, + (u_long)ckp_args->ckp_lsn.offset); + __db_err(lp->dbenv, "Previous checkpoint: [%lu][%lu]", + (u_long)ckp_args->last_ckp.file, + (u_long)ckp_args->last_ckp.offset); + } + last_ckp = next_lsn; + next_lsn = ckp_args->last_ckp; + free(ckp_args); + } while (!IS_ZERO_LSN(next_lsn) && + log_compare(&last_ckp, &ckp_lsn) > 0); + + if (F_ISSET(lp, DB_AM_THREAD)) + free(data.data); + + /* + * At this point, either, next_lsn is ZERO or ckp_lsn is the + * checkpoint lsn and last_ckp is the LSN of the last checkpoint + * before ckp_lsn. If the compare in the loop is still true, then + * next_lsn must be 0 and we need to roll forward from the + * beginning of the log. + */ + if (log_compare(&last_ckp, &ckp_lsn) > 0) { + if ((ret = log_get(lp, &last_ckp, &data, DB_FIRST)) != 0) + return (ret); + if (F_ISSET(lp, DB_AM_THREAD)) + free(data.data); + } + *lsnp = last_ckp; + + if (verbose) + __db_err(lp->dbenv, "Rolling forward from [%lu][%lu]", + (u_long)last_ckp.file, (u_long)last_ckp.offset); + + return (IS_ZERO_LSN(last_ckp) ? DB_NOTFOUND : 0); +} |